RepRap Mendel auto bed leveling

Starting from this idea http://www.thingiverse.com/thing:273805 I have created this version for my RepRap Mendel. It works in the same way and you must follow the instructions from http://www.thingiverse.com/thing:273805. I have used POM 8X10X12 from SKF for linear bearing, M5 nut fixed with M2.5 screw and M2.5 nut. The limit switch is the Z limit switch from Mendel, and it must be inverted (changed) from Normal Closed to Normal Open. The construction is useful not only for auto bed leveling but also for zeroing without the need to adjust/tune the position of limit switch on Z shaft.