Minecraft wiki entry for Trap_design, associated text: Some players have experimented with the ability to pick up an item through a corner. The item is placed on a wooden pressure plate, the deactivation of which creates a signal. The item will disappear after 5 minutes, so the trap is unstable without a pre-trigger complications, but this can be avoided by redispensing it. This trigger also assumes the target has room in their inventory for the item being used. Arrows tend to be used because many players carry arrows and probably wouldn't notice an extra. This trigger is much more hidden than others, almost any corner can be a trigger. A tutorial video explaining this type of trigger is shown below.