Minecraft wiki entry for Trapdoor_uses, associated text: This design can be used with the distributor to make a fully functional wolf caller. By placing a trapdoor above a 1x1 pool of water with a wolf on the trapdoor, if you are the right distance away - when you push the button the wolf will fall in the water and, to prevent itself from drowning, stand up, sense you're away and teleport to you. This design is effective for people who frequently fight monsters. Add the distributor and you can successfully call multiple wolves.