Minecraft wiki entry for Trap_design, associated text: Since our trapper can't maintain the trap consistently without drawing suspicion, let's assume they set up a redstone clock to a dispenser. Every four and a half minutes a new item will be dispensed, maintaining the trap. Clocks are generally a complication, but since it is used to stabilize the trigger we'll call it part of the trigger. This trap is hidden in a natural location and uses an invisible trigger (an item through the wall). This opens a flood gate of lava (method) in the entrance, it will spread and trap the explorer in the cave.