diff --git a/src/main/java/com/gtnewhorizon/structurelib/StructureLib.java b/src/main/java/com/gtnewhorizon/structurelib/StructureLib.java
index c441bc40..0d8504e0 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/StructureLib.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/StructureLib.java
@@ -100,6 +100,8 @@ public class StructureLib {
         }
     };
 
+    public static boolean isGTLoaded;
+
     @Mod.EventHandler
     public void preInit(FMLPreInitializationEvent e) {
         ConfigurationHandler.INSTANCE.init(e.getSuggestedConfigurationFile());
@@ -118,6 +120,8 @@ public class StructureLib {
         if (Loader.isModLoaded(STRUCTURECOMPAT_MODID)) {
             COMPAT = Loader.instance().getIndexedModList().get(STRUCTURECOMPAT_MODID).getMod();
         }
+
+        isGTLoaded = Loader.isModLoaded("gregtech");
     }
 
     @Mod.EventHandler
diff --git a/src/main/java/com/gtnewhorizon/structurelib/gui/GuiScreenConfigureChannels.java b/src/main/java/com/gtnewhorizon/structurelib/gui/GuiScreenConfigureChannels.java
index 314c2519..10dcba09 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/gui/GuiScreenConfigureChannels.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/gui/GuiScreenConfigureChannels.java
@@ -25,6 +25,15 @@ import com.gtnewhorizon.structurelib.gui.GuiScrollableList.IGuiScreen;
 
 public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen {
 
+    private static final int ADD_BTN = 0;
+    private static final int UNSET_BTN = 1;
+    private static final int WIPE_BTN = 2;
+    private static final int SHOW_ERROR_BTN = 3;
+    private static final int GT_NO_HATCH_BTN = 4;
+
+    private static final String SHOW_ERROR_CHANNEL = "show_error";
+    private static final String GT_NO_HATCH_CHANNEL = "gt_no_hatch";
+
     private static final int KEY_MAX_WIDTH = 50;
     private final ItemStack trigger;
     private final GuiChannelsList list;
@@ -128,7 +137,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
 
         addButton(
                 new GuiButton(
-                        0,
+                        ADD_BTN,
                         guiLeft + 12,
                         guiTop + 157,
                         47,
@@ -136,7 +145,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
                         I18n.format("item.structurelib.constructableTrigger.gui.add")));
         addButton(
                 new GuiButton(
-                        1,
+                        UNSET_BTN,
                         guiLeft + 65,
                         guiTop + 157,
                         47,
@@ -144,13 +153,27 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
                         I18n.format("item.structurelib.constructableTrigger.gui.unset")));
         addButton(
                 new GuiButton(
-                        2,
+                        WIPE_BTN,
                         guiLeft + 118,
                         guiTop + 157,
                         47,
                         20,
                         I18n.format("item.structurelib.constructableTrigger.gui.wipe")));
 
+        addButton(
+                new GuiButton(
+                        SHOW_ERROR_BTN,
+                        StructureLib.isGTLoaded ? guiLeft + 12 : guiLeft + 52,
+                        guiTop + 180,
+                        73,
+                        20,
+                        ""));
+
+        // only show GT hatch button if GT is loaded
+        if (StructureLib.isGTLoaded) {
+            addButton(new GuiButton(GT_NO_HATCH_BTN, guiLeft + 92, guiTop + 180, 73, 20, ""));
+        }
+
         updateButtons();
     }
 
@@ -171,7 +194,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
 
     @Override
     public int getYSize() {
-        return 188;
+        return 211;
     }
 
     @Override
@@ -250,10 +273,27 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
         // STACKOVERFLOW!
         String keyText = key.getText();
         boolean existing = !StringUtils.isEmpty(keyText) && ChannelDataAccessor.hasSubChannel(trigger, keyText);
-        getButtonList().get(0).displayString = existing ? I18n.format("item.structurelib.constructableTrigger.gui.set")
+        getButtonList().get(ADD_BTN).displayString = existing
+                ? I18n.format("item.structurelib.constructableTrigger.gui.set")
                 : I18n.format("item.structurelib.constructableTrigger.gui.add");
-        getButtonList().get(0).enabled = !StringUtils.isBlank(value.getText());
-        getButtonList().get(1).enabled = existing && !StringUtils.isBlank(value.getText());
+        getButtonList().get(ADD_BTN).enabled = !StringUtils.isBlank(value.getText());
+        getButtonList().get(UNSET_BTN).enabled = existing && !StringUtils.isBlank(value.getText());
+
+        if (ChannelDataAccessor.hasSubChannel(trigger, SHOW_ERROR_CHANNEL)) {
+            getButtonList().get(SHOW_ERROR_BTN).displayString = "Hide Errors";
+        } else {
+            getButtonList().get(SHOW_ERROR_BTN).displayString = "Show Errors";
+        }
+
+        // this button only exists if GT is loaded.
+        if (StructureLib.isGTLoaded) {
+            if (ChannelDataAccessor.hasSubChannel(trigger, GT_NO_HATCH_CHANNEL)) {
+                getButtonList().get(GT_NO_HATCH_BTN).displayString = "Hatches";
+            } else {
+                getButtonList().get(GT_NO_HATCH_BTN).displayString = "No Hatch";
+            }
+        }
+
     }
 
     private int getValue() {
@@ -268,18 +308,35 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
     protected void actionPerformed(GuiButton btn) {
         if (btn == null) return;
         switch (btn.id) {
-            case 0:
+            case ADD_BTN:
                 int value = getValue();
                 if (value <= 0) return;
                 ChannelDataAccessor.setChannelData(trigger, key.getText(), value);
                 break;
-            case 1:
+            case UNSET_BTN:
                 ChannelDataAccessor.unsetChannelData(trigger, key.getText());
                 break;
-            case 2:
+            case WIPE_BTN:
                 ChannelDataAccessor.wipeChannelData(trigger);
                 break;
+            case SHOW_ERROR_BTN:
+                if (ChannelDataAccessor.hasSubChannel(trigger, SHOW_ERROR_CHANNEL)) {
+                    ChannelDataAccessor.unsetChannelData(trigger, SHOW_ERROR_CHANNEL);
+                } else {
+                    ChannelDataAccessor.setChannelData(trigger, SHOW_ERROR_CHANNEL, 1);
+                }
+                break;
+            case GT_NO_HATCH_BTN:
+                if (ChannelDataAccessor.hasSubChannel(trigger, GT_NO_HATCH_CHANNEL)) {
+                    ChannelDataAccessor.unsetChannelData(trigger, GT_NO_HATCH_CHANNEL);
+                } else {
+                    ChannelDataAccessor.setChannelData(trigger, GT_NO_HATCH_CHANNEL, 1);
+                }
+                break;
         }
+
+        updateButtons();
+
         super.actionPerformed(btn);
     }
 
@@ -350,6 +407,7 @@ public class GuiScreenConfigureChannels extends GuiScreen implements IGuiScreen
                 Entry<String, Integer> e = getElementAt(elementIndex);
                 if (e != null) {
                     ChannelDataAccessor.unsetChannelData(trigger, e.getKey());
+                    updateButtons();
                     return false;
                 }
             }
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureDefinition.java b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureDefinition.java
index 8c152071..2b6b7732 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureDefinition.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureDefinition.java
@@ -12,6 +12,7 @@ import net.minecraft.world.World;
 
 import com.gtnewhorizon.structurelib.StructureLib;
 import com.gtnewhorizon.structurelib.StructureLibAPI;
+import com.gtnewhorizon.structurelib.alignment.constructable.ChannelDataAccessor;
 import com.gtnewhorizon.structurelib.alignment.constructable.ISurvivalConstructable;
 import com.gtnewhorizon.structurelib.alignment.enumerable.ExtendedFacing;
 
@@ -50,7 +51,7 @@ import com.gtnewhorizon.structurelib.alignment.enumerable.ExtendedFacing;
  * itself.</li>
  * <li>The "C" position would be the number of blocks between you and controller, not counting controller itself.</li>
  * </ul>
- * 
+ *
  * @param <T> Type of the context object. Usually this will be the multiblock controller.
  */
 public interface IStructureDefinition<T> {
@@ -72,7 +73,7 @@ public interface IStructureDefinition<T> {
 
     /**
      * Run a structure check.
-     * 
+     *
      * @param object              context object. usually multiblock controller.
      * @param piece               the structure piece's string identifier.
      * @param world               the world object this check takes place in.
@@ -107,7 +108,7 @@ public interface IStructureDefinition<T> {
 
     /**
      * Spawn hint particles. Should not be called on server side.
-     * 
+     *
      * @param object         context object. usually multiblock controller.
      * @param piece          the structure piece's string identifier.
      * @param world          the world object this check takes place in.
@@ -320,7 +321,7 @@ public interface IStructureDefinition<T> {
 
     /**
      * Low level utility.
-     * 
+     *
      * @param object                                  context object. usually multiblock controller.
      * @param trigger                                 The trigger item that contains channel data.
      * @param elements                                the structure piece
@@ -394,6 +395,10 @@ public interface IStructureDefinition<T> {
                         basePositionC,
                         ignoreBlockUnloaded((e, w, x, y, z, a, b, c) -> {
                             e.spawnHint(object, world, x, y, z, trigger);
+                            if (ChannelDataAccessor.hasSubChannel(trigger, "show_error")
+                                    && !e.couldBeValid(object, world, x, y, z, trigger)) {
+                                StructureLibAPI.markHintParticleError(StructureLib.getCurrentPlayer(), world, x, y, z);
+                            }
                             return true;
                         }),
                         "spawnHint");
@@ -420,7 +425,7 @@ public interface IStructureDefinition<T> {
 
     /**
      * Create a new instance of builder.
-     * 
+     *
      * @param <T> type of context object
      */
     static <T> StructureDefinition.Builder<T> builder() {
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElement.java b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElement.java
index eb16fcc5..63d1b4b7 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElement.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElement.java
@@ -32,6 +32,16 @@ public interface IStructureElement<T> {
 
     boolean check(T t, World world, int x, int y, int z);
 
+    /**
+     * Pure (stateless and side effect free) function to test if current block could be valid. Used to give user hints
+     * about incorrectly placed blocks given a controller and trigger item. If couldBeValid(...) == false for a set of
+     * channels, with those same tiers, check(...) == false. Not required, defaults to true which is always safe but
+     * won't give the user error hints.
+     */
+    default boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+        return true;
+    }
+
     boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger);
 
     boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger);
@@ -185,6 +195,11 @@ public interface IStructureElement<T> {
                 return IStructureElement.this.check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return IStructureElement.this.couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return IStructureElement.this.spawnHint(t, world, x, y, z, trigger);
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementChain.java b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementChain.java
index 819990fd..c527c76a 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementChain.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementChain.java
@@ -31,6 +31,16 @@ public interface IStructureElementChain<T> extends IStructureElement<T> {
         return false;
     }
 
+    @Override
+    default boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+        for (IStructureElement<T> fallback : fallbacks()) {
+            if (fallback.couldBeValid(t, world, x, y, z, trigger)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
     @Override
     default boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
         for (IStructureElement<T> fallback : fallbacks()) {
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementCheckOnly.java b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementCheckOnly.java
index 03f2b859..ee8144a5 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementCheckOnly.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureElementCheckOnly.java
@@ -14,6 +14,11 @@ public interface IStructureElementCheckOnly<T> extends IStructureElement<T> {
         return false;
     }
 
+    @Override
+    default boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+        return true;
+    }
+
     @Override
     default boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
         return false;
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureNavigate.java b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureNavigate.java
index 6ce52c52..602a4993 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureNavigate.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/IStructureNavigate.java
@@ -17,6 +17,11 @@ interface IStructureNavigate<T> extends IStructureElement<T> {
         return true;
     }
 
+    @Override
+    default boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+        return true;
+    }
+
     @Override
     default boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
         return true;
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java b/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java
index 3f8cfda3..0959ee67 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/LazyStructureElement.java
@@ -32,6 +32,11 @@ class LazyStructureElement<T> implements IStructureElementDeferred<T> {
         return get(t).check(t, world, x, y, z);
     }
 
+    @Override
+    public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+        return get(t).couldBeValid(t, world, x, y, z, trigger);
+    }
+
     @Override
     public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
         return get(t).placeBlock(t, world, x, y, z, trigger);
diff --git a/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java b/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
index a6baa3c9..f44e3095 100644
--- a/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
+++ b/src/main/java/com/gtnewhorizon/structurelib/structure/StructureUtility.java
@@ -155,6 +155,11 @@ public class StructureUtility {
             return world.isAirBlock(x, y, z);
         }
 
+        @Override
+        public boolean couldBeValid(Object t, World world, int x, int y, int z, ItemStack trigger) {
+            return check(t, world, x, y, z);
+        }
+
         @Override
         public boolean spawnHint(Object o, World world, int x, int y, int z, ItemStack trigger) {
             StructureLibAPI.hintParticle(world, x, y, z, StructureLibAPI.getBlockHint(), 13);
@@ -186,6 +191,11 @@ public class StructureUtility {
             return !world.isAirBlock(x, y, z);
         }
 
+        @Override
+        public boolean couldBeValid(Object t, World world, int x, int y, int z, ItemStack trigger) {
+            return check(t, world, x, y, z);
+        }
+
         @Override
         public boolean spawnHint(Object o, World world, int x, int y, int z, ItemStack trigger) {
             StructureLibAPI.hintParticle(world, x, y, z, StructureLibAPI.getBlockHint(), 14);
@@ -225,6 +235,11 @@ public class StructureUtility {
             return false;
         }
 
+        @Override
+        public boolean couldBeValid(Object t, World world, int x, int y, int z, ItemStack trigger) {
+            return check(t, world, x, y, z);
+        }
+
         @Override
         public boolean spawnHint(Object o, World world, int x, int y, int z, ItemStack trigger) {
             StructureLibAPI.hintParticle(world, x, y, z, StructureLibAPI.getBlockHint(), 15);
@@ -479,6 +494,11 @@ public class StructureUtility {
                 return true;
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, StructureLibAPI.getBlockHint(), meta);
@@ -499,6 +519,11 @@ public class StructureUtility {
                 return true;
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, icons.get());
@@ -519,6 +544,11 @@ public class StructureUtility {
                 return true;
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticleTinted(world, x, y, z, icons.get(), RGBa);
@@ -667,9 +697,23 @@ public class StructureUtility {
             }
 
             private Pair<Block, Integer> getHint(ItemStack trigger) {
+                if (hints.isEmpty()) return null;
                 return hints.get(Math.min(Math.max(trigger.stackSize, 1), hints.size()) - 1);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                Pair<Block, Integer> hint = getHint(trigger);
+                if (hint == null) return true;
+                TIER hintTier = tierExtractor.convert(hint.getKey(), hint.getValue());
+                Block block = world.getBlock(x, y, z);
+                int meta = world.getBlockMetadata(x, y, z);
+                TIER worldTier = tierExtractor.convert(block, meta);
+
+                // if the block is in the same tier as the hint block, this could be valid
+                return Objects.equals(hintTier, worldTier);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 Pair<Block, Integer> hint = getHint(trigger);
@@ -767,6 +811,11 @@ public class StructureUtility {
                 return world.getBlock(x, y, z) == getBlock() && (wildcard || world.getBlockMetadata(x, y, z) == meta);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 if (getBlock() == null) return error().spawnHint(t, world, x, y, z, trigger);
@@ -841,10 +890,16 @@ public class StructureUtility {
 
             @Override
             public boolean check(T t, World world, int x, int y, int z) {
-                if (init()) return world.getBlock(x, y, z) != block && world.getBlockMetadata(x, y, z) == meta;
+                if (init()) return world.getBlock(x, y, z) == block && world.getBlockMetadata(x, y, z) == meta;
                 else return fallback.check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                if (init()) return world.getBlock(x, y, z) == block && world.getBlockMetadata(x, y, z) == meta;
+                else return fallback.couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 if (init()) {
@@ -921,6 +976,11 @@ public class StructureUtility {
                 return blocsMap.getOrDefault(worldBlock, MIN_VALUE) == worldBlock.getDamageValue(world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -958,6 +1018,11 @@ public class StructureUtility {
                         .contains(worldBlock.getDamageValue(world, x, y, z));
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -982,6 +1047,11 @@ public class StructureUtility {
                 return block == worldBlock && meta == worldBlock.getDamageValue(world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return check(t, world, x, y, z);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -1016,6 +1086,13 @@ public class StructureUtility {
                 return iBlockAdder.apply(t, worldBlock, worldBlock.getDamageValue(world, x, y, z));
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                // calling iBlockAdder can potentially modify external state
+                // therefore we assume this can always be valid.
+                return true;
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -1049,6 +1126,11 @@ public class StructureUtility {
                     return blocsMap.getOrDefault(worldBlock, MIN_VALUE) == worldBlock.getDamageValue(world, x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     ((ICustomBlockSetting) defaultBlock).setBlock(world, x, y, z, defaultMeta);
@@ -1093,6 +1175,11 @@ public class StructureUtility {
                     return blocsMap.getOrDefault(worldBlock, MIN_VALUE) == worldBlock.getDamageValue(world, x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     world.setBlock(x, y, z, defaultBlock, defaultMeta, 2);
@@ -1158,6 +1245,11 @@ public class StructureUtility {
                             .contains(worldBlock.getDamageValue(world, x, y, z));
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     ((ICustomBlockSetting) defaultBlock).setBlock(world, x, y, z, defaultMeta);
@@ -1203,6 +1295,11 @@ public class StructureUtility {
                             .contains(worldBlock.getDamageValue(world, x, y, z));
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     world.setBlock(x, y, z, defaultBlock, defaultMeta, 2);
@@ -1260,6 +1357,11 @@ public class StructureUtility {
                     return block == worldBlock && meta == worldBlock.getDamageValue(world, x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     ((ICustomBlockSetting) defaultBlock).setBlock(world, x, y, z, defaultMeta);
@@ -1287,6 +1389,11 @@ public class StructureUtility {
                     return block == worldBlock && meta == worldBlock.getDamageValue(world, x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     world.setBlock(x, y, z, defaultBlock, defaultMeta, 2);
@@ -1323,6 +1430,11 @@ public class StructureUtility {
                     return block == world.getBlock(x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     ((ICustomBlockSetting) defaultBlock).setBlock(world, x, y, z, defaultMeta);
@@ -1350,6 +1462,11 @@ public class StructureUtility {
                     return block == world.getBlock(x, y, z);
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    return check(t, world, x, y, z);
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     world.setBlock(x, y, z, defaultBlock, defaultMeta, 2);
@@ -1416,6 +1533,13 @@ public class StructureUtility {
                     return iBlockAdder.apply(t, worldBlock, worldBlock.getDamageValue(world, x, y, z));
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    // calling iBlockAdder can potentially modify external state
+                    // therefore we assume this can always be valid.
+                    return true;
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     ((ICustomBlockSetting) defaultBlock).setBlock(world, x, y, z, defaultMeta);
@@ -1455,6 +1579,13 @@ public class StructureUtility {
                     return iBlockAdder.apply(t, worldBlock, worldBlock.getDamageValue(world, x, y, z));
                 }
 
+                @Override
+                public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                    // calling iBlockAdder can potentially modify external state
+                    // therefore we assume this can always be valid.
+                    return true;
+                }
+
                 @Override
                 public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                     world.setBlock(x, y, z, defaultBlock, defaultMeta, 2);
@@ -1510,6 +1641,13 @@ public class StructureUtility {
                 return iTileAdder.apply(t, tileEntity);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                // calling iTileAdder can potentially modify external state
+                // therefore we assume this can always be valid.
+                return true;
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -1536,6 +1674,13 @@ public class StructureUtility {
                 return tileClass.isInstance(tileEntity) && iTileAdder.test(t, tileClass.cast(tileEntity));
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                // calling iTileAdder can potentially modify external state
+                // therefore we assume this can always be valid.
+                return true;
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 StructureLibAPI.hintParticle(world, x, y, z, hintBlock, hintMeta);
@@ -1569,6 +1714,11 @@ public class StructureUtility {
                 return check;
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return element.couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return element.placeBlock(t, world, x, y, z, trigger);
@@ -1620,6 +1770,11 @@ public class StructureUtility {
                 return check;
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return element.couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return element.placeBlock(t, world, x, y, z, trigger);
@@ -1678,6 +1833,13 @@ public class StructureUtility {
                 return predicate.test(t) && downstream.check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                // this COULD potentially impact external state
+                // but predicate really should not have side effects
+                return predicate.test(t) && downstream.couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return predicate.test(t) && downstream.spawnHint(t, world, x, y, z, trigger);
@@ -1774,6 +1936,11 @@ public class StructureUtility {
                 return elem.check(t.getCurrentContext(), world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return elem.couldBeValid(t.getCurrentContext(), world, x, y, z, trigger);
+            }
+
             @Override
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return elem.spawnHint(t.getCurrentContext(), world, x, y, z, trigger);
@@ -1861,6 +2028,11 @@ public class StructureUtility {
                 return to.get().check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return to.get().couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return to.get().placeBlock(t, world, x, y, z, trigger);
@@ -1914,6 +2086,11 @@ public class StructureUtility {
                 return to.apply(t).check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return to.apply(t).couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return to.apply(t).placeBlock(t, world, x, y, z, trigger);
@@ -2126,6 +2303,11 @@ public class StructureUtility {
                 return to.apply(t, null).check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return to.apply(t, trigger).couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return to.apply(t, trigger).placeBlock(t, world, x, y, z, trigger);
@@ -2318,6 +2500,11 @@ public class StructureUtility {
                 return toCheck.apply(t).check(t, world, x, y, z);
             }
 
+            @Override
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                return to.apply(t, trigger).couldBeValid(t, world, x, y, z, trigger);
+            }
+
             @Override
             public boolean placeBlock(T t, World world, int x, int y, int z, ItemStack trigger) {
                 return to.apply(t, trigger).placeBlock(t, world, x, y, z, trigger);
@@ -2562,6 +2749,11 @@ public class StructureUtility {
                 return backing.check(t, world, x, y, z);
             }
 
+            public boolean couldBeValid(T t, World world, int x, int y, int z, ItemStack trigger) {
+                ItemStack newTrigger = ChannelDataAccessor.withChannel(trigger, channel);
+                return backing.couldBeValid(t, world, x, y, z, newTrigger);
+            }
+
             public boolean spawnHint(T t, World world, int x, int y, int z, ItemStack trigger) {
                 ItemStack newTrigger = ChannelDataAccessor.withChannel(trigger, channel);
                 // We know spawnHint will only be called on client side, so the lack of player isn't quite an issue
diff --git a/src/main/resources/assets/structurelib/textures/gui/channels.png b/src/main/resources/assets/structurelib/textures/gui/channels.png
index c76cdf33..4726863d 100644
Binary files a/src/main/resources/assets/structurelib/textures/gui/channels.png and b/src/main/resources/assets/structurelib/textures/gui/channels.png differ