The fourth part in the gravity block door series, the 8x8 version is the biggest possible with continuous side block-elevators. What makes this version different is the double block-elevators on each side, which speeds the door up significantly. Considering that 64 blocks need to be moved up this makes a huge difference.

This door drops the gravity blocks (concrete, sand or gravel) and pushes them up on the sides. Afterwards they will fall down again to close the door. It mixes up the patterns.

Feel free to use this however you want, or use the concept for other builds.