So, this is the final part in making the trap. Under the blocks connected to the pistons, dig a pit going straight down. After about 5 blocks, put some lava in the bottom to burn the victim and his stuff, or keep on digging about 30-100 blocks, around 30 for unarmed people, and 100 for the heavily armed people. If you want, you can add some cacti to the bottom to kill them if they aren't dead already. Then make a tunnel about 10 blocks long then dig up, adding ladders as you go. This way, you can enter the pit after someone falls in to steal their stuff. Cover the entrance so nobody finds it. And there you go! Just make sure to replace the bait if it's gone and the redstone torch after each time the trap works.