Introduction: Redstone Trap
Here is how to build a relatively easy redstone trap.
Step 1:
Dig a hole 5x5x2.
Step 2:
Put sticky pistons against the edges of the hole, don't do the corners it's pointless, then on the inside of the sticky pistons, use redstone dust to connect them.
Step 3:
Fill it all in with whatever block you want that can be pushed.
Step 4:
Put pressure plates one in from the edge, even though you avoided the pistons in the corner still put pressure plates on the corners.
Step 5:
Put 3 high pillars in the corners, then make a roof, make sure you can't jump inside the structure.
Step 6:
Put a chest in the middle and fill it with whatever you want, I used diamonds.
Step 7:
There you have it. A trap. Make sure the pressure plates match the floor, I used something different so you guys could see.