M8 Nut and Screw

In fact, this is a Z Endstop Trigger for the 3 Points Leveling for Makerbot Replicator... ( http://www.thingiverse.com/thing:106474 )

Together with the thing mentioned above, it makes it very easy to switch between different thickness of glasses or not glass at all or this tape or the other...

...once the platform is level, just choose the build surface you'd like to use and adjust the endstop trigger accordinly, no need to level anything again!

The OpenSCAD scripts I used are not avail