Orientable Thumbscrews

I'm using some thumbscrews http://www.thingiverse.com/thing:13778 to make my makebot platform level, which works great. However, I just keep rotating the screws in wrong direction, especially whem I'm doing it with left hand. So, I modified the thumbscrew design a little bit. I replaced the symmetric teeth with two non symmetric shapes, so I can tell which direction to rotate simply by touching it.