Prusa i3 auto bed leveling

So this is a bit modified version of the http://www.thingiverse.com/thing:756948 which i modified to be able to use a standard 9G servo and a photo sensor I had laying at home (http://www.dx.com/p/2-channel-speed-sensor-module-for-arduino-blue-151225#.VTgAvpNi9ZQ). For the rod I used a standard 3.7mm nail which I cut off the head and shortened it so that it fits my Prusa i3.