Minecraft wiki entry for Piston_uses, associated text: When triggered, the section of the floor is withdrawn from below the target. This design is best used inside to hide the pistons and circuitry. This can easily be added to a tunnel. Under the floor, dig out a 2-block deep pit for each of the trap blocks you want to move. Mine out two blocks horizontally from each space where the trap floor goes and put a sticky piston at the back of each hole. In front of the sticky piston, replace the floor blocks (make sure that the trap block is the same as the regular floor blocks so as not to cause suspicion. In the space beneath the floor can be a long drop, lava, dispensers filled with arrows. For simplicity, we chose lava.