This is version four of my Ground Piston Door found here. This version is designed for people with more vertical space than horizontal space. For example, if you play on a SMP server with the Towny plugin and plots are small. The over-all design is only about 1 block thinner on each side but every block counts.

This one uses a T Flip-Flop instead of a monostable circuit because the monostable circuit design ended up using more space and I didn't see a benefit to it. The pistons are powered from below using a torch ladder instead of from the side. Simple change but it required a complete redesign of the wiring.

Version 1: Click Here
Version 2: Click Here
Version 3: Click Here

Additional Notes

Thanks to EnderKhaos for helping make the locking mechanism.