Minecraft wiki entry for Music_disc_farming, associated text: This design uses pistons to trap the skeleton and creeper in one spot. As shown in the video, to use this trap, you must first lure a skeleton into place onto the pressure plate of one of the traps shown in the schematic. Once that is done, you should weaken a creeper and lure into a second chamber. Finally, you should be able to stand behind the creeper and cause the skeleton to deliver the finishing blows.