This is done in Snapshot 13w10b. Setting up a clock linking up to a sticky piston. 2 blocks away from the face of the sticky piston. Place a piece of glass block on the floor. Put any block (Wood planks, cobblestone, etc) next to the glass (3 blocks away from the piston). Then put a rail on top of the block. Then place the same type of rail on the block 1 block away from the sticky piston (before the glass block). And sometimes, the block will be pushed further and turn into a visual glitch (Doesn't drop item is broken) and the place of the original place of the block will be replaced by a rail, but floating. Reloading the world will fix this.