Minecraft wiki entry for Piston_uses, associated text: Triggering this is best done with a pressure plate, however, this can be difficult to hide from other players. You need to wire the pressure plate to the input of a NOT-gate and the pistons to the output. A delay can be helpful to ensure the player is over the right blocks when the trap triggers, which can be accomplished by putting in redstone repeaters. Stone pressure plates triggers only when players or mobs walk over, whereas wooden pressure plates trigger also for dropped items. Metal pressure plates act differently still. This trap is reset once the signal from the pressure plates is disabled.