Introduction: Basic Piston Door
I found this while experimenting with pistons
Step 1: You Will Need:
2 sticky pistons, 1 lever, 4 blocks of choice (not obsidian) and a redstone torch
Step 2: Pistons and Blocks
Place the blocks and pistons as shown in the picture
Step 3: Add the Redstone Torch and Lever
Add the redstone torch and lever as shown
Step 4: Lever Usage
The door will open and close upon hitting the lever