Panels!

Panels are thin trapdoor like blocks, but instead of flipping only 90 degrees, they flip 90 degrees every time you right click them, or until they hit a wall. This could make it so that you could make working window shutters, and they could act as a million things in machines for more technical redstone players. Panels would be crafted with four wood and two iron, like a smithing table on it's side, and it would yield four.