Minecraft wiki entry for Block_and_item_duplication, associated text: Shulker Box dupe allows you to duplicate any item in Minecraft singleplayer or Realms. This glitch works with 2 players or with an auto mine mod. So you quickly spam your item in and out while it being broken. The key is to take the item out just before the shulker box breaks. This may take a few tries but eventually you will dupe your items.