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.