See the Imgur link for an animation. When upside down sticky pistons are powered and then retracted from the block above with redstone on top, it will cause it to duplicate the horizontal piston it moves. Also, there seems to be a disconnected floating horizontal piston arm when the top piston is powered. Works when both sticky and nonstick pistons are moved in this way. On a related note, when the top pistons move upside down pistons in the same way, it causes some other strange arm glitches.