diff --git a/src/main/java/codechicken/multipart/api/ItemMultipart.java b/src/main/java/codechicken/multipart/api/ItemMultipart.java
index 45fc3b3..31d10e9 100644
--- a/src/main/java/codechicken/multipart/api/ItemMultipart.java
+++ b/src/main/java/codechicken/multipart/api/ItemMultipart.java
@@ -12,6 +12,9 @@
 import net.minecraft.world.level.block.SoundType;
 import org.jetbrains.annotations.Nullable;
 
+import java.util.Collection;
+import java.util.Collections;
+
 /**
  * Created by covers1624 on 1/1/21.
  */
@@ -24,6 +27,10 @@ public ItemMultipart(Properties properties) {
     @Nullable
     public abstract MultiPart newPart(MultipartPlaceContext context);
 
+    protected Collection<MultiPart> newParts(MultipartPlaceContext context) {
+        return Collections.singletonList(newPart(context));
+    }
+
     @Override
     public InteractionResult useOn(UseOnContext context) {
 
@@ -39,18 +46,21 @@ private boolean place(MultipartPlaceContext context) {
         Level world = context.getLevel();
         BlockPos pos = context.getClickedPos();
 
-        MultiPart part = newPart(context);
-        if (part == null || !TileMultipart.canPlacePart(context, part)) return false;
+        Collection<MultiPart> parts = newParts(context);
+        if (parts.isEmpty() || !TileMultipart.canPlaceParts(context, parts)) return false;
 
         if (!world.isClientSide) {
-            TileMultipart.addPart(world, pos, part);
-            SoundType sound = part.getPlacementSound(context);
-            if (sound != null) {
+            for (MultiPart part : parts) {
+                TileMultipart.addPart(world, pos, part);
+
+                SoundType sound = part.getPlacementSound(context);
+                if (sound == null) continue;
+
                 world.playSound(null, pos, sound.getPlaceSound(),
                         SoundSource.BLOCKS, (sound.getVolume() + 1.0F) / 2.0F, sound.getPitch() * 0.8F);
             }
         }
-        if (!context.getPlayer().getAbilities().instabuild) {
+        if (!context.getPlayer().isCreative()) {
             context.getItemInHand().shrink(1);
         }
         return true;
diff --git a/src/main/java/codechicken/multipart/block/TileMultipart.java b/src/main/java/codechicken/multipart/block/TileMultipart.java
index 19848f9..6b677e0 100644
--- a/src/main/java/codechicken/multipart/block/TileMultipart.java
+++ b/src/main/java/codechicken/multipart/block/TileMultipart.java
@@ -15,7 +15,6 @@
 import codechicken.multipart.network.MultiPartSPH;
 import codechicken.multipart.util.*;
 import com.google.common.base.Preconditions;
-import net.covers1624.quack.collection.ColUtils;
 import net.covers1624.quack.collection.FastStream;
 import net.minecraft.core.BlockPos;
 import net.minecraft.core.Direction;
@@ -46,6 +45,7 @@
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.List;
 import java.util.concurrent.CopyOnWriteArrayList;
 import java.util.function.Consumer;
@@ -234,8 +234,15 @@ public void writeDesc(MCDataOutput packet) {
 
     //region *** Adding/Removing parts ***
 
-    public boolean canAddPart(MultiPart part) {
-        return !partList.contains(part) && occlusionTest(partList, part);
+    public final boolean canAddPart(MultiPart part) {
+        return canAddParts(Collections.singletonList(part));
+    }
+
+    public boolean canAddParts(Iterable<MultiPart> parts) {
+        for (MultiPart part : parts) {
+            if (partList.contains(part)) return false;
+        }
+        return occlusionTest(partList, parts);
     }
 
     /**
@@ -251,11 +258,18 @@ public boolean canReplacePart(MultiPart oPart, MultiPart nPart) {
         if (oPart != nPart && partList.contains(nPart)) {
             return false;
         }
-        return occlusionTest(FastStream.of(partList).filter(e -> e != oPart), nPart);
+        return occlusionTest(FastStream.of(partList).filter(e -> e != oPart), Collections.singletonList(nPart));
     }
 
-    public boolean occlusionTest(Iterable<MultiPart> parts, MultiPart nPart) {
-        return ColUtils.allMatch(parts, part -> part.occlusionTest(nPart) && nPart.occlusionTest(part));
+    public boolean occlusionTest(Iterable<MultiPart> parts, Iterable<MultiPart> newParts) {
+        for (MultiPart oldPart : parts) {
+            for (MultiPart newPart : newParts) {
+                if (!oldPart.occlusionTest(newPart) || !newPart.occlusionTest(oldPart)) {
+                    return false;
+                }
+            }
+        }
+        return true;
     }
 
     public void addPart_impl(MultiPart part) {
@@ -607,16 +621,22 @@ public CapabilityCache getCapCache() {
     //endregion
 
     public static boolean canPlacePart(UseOnContext context, MultiPart part) {
+        return canPlaceParts(context, Collections.singletonList(part));
+    }
+
+    public static boolean canPlaceParts(UseOnContext context, Iterable<MultiPart> parts) {
         Level level = context.getLevel();
         BlockPos pos = context.getClickedPos();
 
-        if (!isUnobstructed(level, pos, part)) {
-            return false;
+        for (MultiPart p : parts) {
+            if (!isUnobstructed(level, pos, p)) {
+                return false;
+            }
         }
 
         TileMultipart tile = MultipartHelper.getOrConvertTile(level, pos);
         if (tile != null) {
-            return tile.canAddPart(part);
+            return tile.canAddParts(parts);
         }
 
         if (!replaceable(level, pos, context)) return false;
diff --git a/src/main/java/codechicken/multipart/trait/TPartialOcclusionTile.java b/src/main/java/codechicken/multipart/trait/TPartialOcclusionTile.java
index 817c160..e371f78 100644
--- a/src/main/java/codechicken/multipart/trait/TPartialOcclusionTile.java
+++ b/src/main/java/codechicken/multipart/trait/TPartialOcclusionTile.java
@@ -3,6 +3,8 @@
 import codechicken.multipart.api.part.MultiPart;
 import codechicken.multipart.api.part.PartialOcclusionPart;
 import codechicken.multipart.block.TileMultipart;
+import net.covers1624.quack.collection.ColUtils;
+import net.covers1624.quack.collection.FastStream;
 import net.minecraft.core.BlockPos;
 import net.minecraft.world.level.block.state.BlockState;
 import net.minecraft.world.phys.shapes.BooleanOp;
@@ -10,8 +12,8 @@
 import net.minecraft.world.phys.shapes.VoxelShape;
 import org.jetbrains.annotations.Nullable;
 
-import java.util.LinkedList;
 import java.util.List;
+import java.util.Set;
 
 /**
  * Implementation for the partial occlusion test.
@@ -24,7 +26,7 @@ public class TPartialOcclusionTile extends TileMultipart {
     @Nullable
     private static TPartialOcclusionTile lastOcclusionTestedTile;
     @Nullable
-    private static VoxelShape lastOcclusionTestedShape;
+    private static Set<VoxelShape> lastOcclusionTestedShape;
     private static boolean lastOcclusionTestedResult;
 
     public TPartialOcclusionTile(BlockPos pos, BlockState state) {
@@ -50,30 +52,31 @@ public void partRemoved(MultiPart remPart, int p) {
     }
 
     @Override
-    public boolean occlusionTest(Iterable<MultiPart> parts, MultiPart npart) {
-        if (npart instanceof PartialOcclusionPart newPart) {
-            VoxelShape newShape = newPart.getPartialOcclusionShape();
-            if (lastOcclusionTestedTile != this || lastOcclusionTestedShape != newShape) {
+    public boolean occlusionTest(Iterable<MultiPart> parts, Iterable<MultiPart> newParts) {
+
+        if (ColUtils.anyMatch(newParts, e -> e instanceof PartialOcclusionPart)) {
+            Set<VoxelShape> newPartialShapes = FastStream.of(newParts)
+                    .filter(e -> e instanceof PartialOcclusionPart)
+                    .map(e -> ((PartialOcclusionPart) e).getPartialOcclusionShape())
+                    .toImmutableSet();
+            if (lastOcclusionTestedTile != this || newPartialShapes.equals(lastOcclusionTestedShape)) {
                 lastOcclusionTestedTile = this;
-                lastOcclusionTestedShape = newShape;
-                lastOcclusionTestedResult = partialOcclusionTest(parts, newPart);
+                lastOcclusionTestedShape = newPartialShapes;
+                lastOcclusionTestedResult = partialOcclusionTest(FastStream.concat(parts, newParts));
             }
             if (!lastOcclusionTestedResult) {
                 return false;
             }
         }
 
-        return super.occlusionTest(parts, npart);
-    }
+        return super.occlusionTest(parts, newParts);    }
 
-    private static boolean partialOcclusionTest(Iterable<MultiPart> allParts, PartialOcclusionPart newPart) {
-        List<PartialOcclusionPart> parts = new LinkedList<>();
-        for (MultiPart part : allParts) {
-            if (part instanceof PartialOcclusionPart) {
-                parts.add((PartialOcclusionPart) part);
-            }
-        }
-        parts.add(newPart);
+    // Returns true if part list satisfies partial occlusion rules
+    private static boolean partialOcclusionTest(FastStream<MultiPart> allParts) {
+        List<PartialOcclusionPart> parts = allParts
+                .filter(e -> e instanceof PartialOcclusionPart)
+                .map(e -> ((PartialOcclusionPart) e))
+                .toList();
 
         for (PartialOcclusionPart part1 : parts) {
             if (part1.allowCompleteOcclusion()) {
diff --git a/src/main/java/codechicken/multipart/trait/TSlottedTile.java b/src/main/java/codechicken/multipart/trait/TSlottedTile.java
index 2468b82..4c780dc 100644
--- a/src/main/java/codechicken/multipart/trait/TSlottedTile.java
+++ b/src/main/java/codechicken/multipart/trait/TSlottedTile.java
@@ -51,17 +51,25 @@ public void partRemoved(MultiPart part, int p) {
     }
 
     @Override
-    public boolean canAddPart(MultiPart part) {
-        if (part instanceof SlottedPart) {
-            int mask = ((SlottedPart) part).getSlotMask();
-            for (int i = 0; i < v_partMap.length; i++) {
-                if ((mask & 1 << i) != 0 && getSlottedPart(i) != null) {
-                    return false;
-                }
+    public boolean canAddParts(Iterable<MultiPart> parts) {
+        // Check collisions among new parts
+        int mask = 0;
+        for (var p : parts) {
+            if (!(p instanceof SlottedPart sp)) continue;
+
+            int partMask = sp.getSlotMask();
+            if ((mask & partMask) != 0) return false;
+            mask |= partMask;
+        }
+
+        // Check collisions of new mask with existing parts
+        for (int i = 0; i < v_partMap.length; i++) {
+            if ((mask & 1 << i) != 0 && getSlottedPart(i) != null) {
+                return false;
             }
         }
 
-        return super.canAddPart(part);
+        return super.canAddParts(parts);
     }
 
     @Override