Minecraft wiki entry for Skeleton_horse_farming, associated text: There needs to be a way of attracting lightning from thunderstorms to spawn skeleton trap horses, (lightning rods will not spawn skeleton trap horses[1]) and the skeleton trap horses will spawn and get pushed to an area near the player, which will spawn 4 skeletons riding 4 skeleton horses. The skeletons can be killed by the player, which is in a safe location, and then the player can push a button which will open iron trapdoors underneath the horses and transport them to an area which they can be stored.