Should fix #267

PlotSquared/src/main/java/com/intellectualcrafters/plot/commands/Set.java

@@ -240,6 +240,12 @@ public class Set extends SubCommand {
                             return true;
                         }
                         blocks = new PlotBlock[] { new PlotBlock((short) BlockManager.manager.getBlockIdFromString(args[1]), (byte) 0) };
+                        for (PlotBlock block : blocks) {
+                            if (!BlockManager.manager.isBlockSolid(block)) {
+                                MainUtil.sendMessage(plr, C.NOT_VALID_BLOCK);
+                                return false;
+                            }
+                        }
                     } catch (final Exception e2) {
                         MainUtil.sendMessage(plr, C.NOT_VALID_BLOCK);
                         return false;

PlotSquared/src/main/java/com/intellectualcrafters/plot/util/BlockManager.java

@@ -6,6 +6,8 @@ import com.intellectualcrafters.plot.object.schematic.PlotItem;
 
 public abstract class BlockManager {
     public static BlockManager manager;
+    
+    public abstract boolean isBlockSolid(PlotBlock block);
 
     public abstract String[] getBiomeList();
     

PlotSquared/src/main/java/com/intellectualcrafters/plot/util/SchematicHandler.java

@@ -183,6 +183,17 @@ public abstract class SchematicHandler {
             }
         }
         final File file = new File(PlotSquared.IMP.getDirectory() + File.separator + "schematics" + File.separator + name + ".schematic");
+        return getSchematic(file);
+    }
+    
+    /**
+     * Get a schematic
+     *
+     * @param name to check
+     *
+     * @return schematic if found, else null
+     */
+    public Schematic getSchematic(File file) {
         if (!file.exists()) {
             PlotSquared.log(file.toString() + " doesn't exist");
             return null;

PlotSquared/src/main/java/com/intellectualcrafters/plot/util/bukkit/BukkitUtil.java

@@ -293,4 +293,15 @@ public class BukkitUtil extends BlockManager {
         return false;
         
     }
+
+    @Override
+    public boolean isBlockSolid(PlotBlock block) {
+        try {
+            Material material = Material.getMaterial(block.id);
+            return material.isBlock() && material.isSolid() && material.isOccluding() && !material.hasGravity();
+        }
+        catch (Exception e) {
+            return false;
+        }
+    }
 }