Minecraft wiki entry for Piston_uses, associated text: is a video of it in action. The basic idea is the same except the torches are placed on the wall above the pistons, and you use a piston facing to each side not just one. There are two positions to place the torches: above the side-facing piston that touches the sticky piston, and above the forward facing piston. As they are wall mounted, placing the torch above the side-facing piston powers both side-facing pistons as well as the sticky piston, saving time.