super simple clip-on probe for use with newly released Printrbot auto leveling firmware. good luck! I printed this is in PLA, and with solid infill. Do as you wish. Printrbot Marlin firmware can be found at https://github.com/Printrbot/Marlin/releases with further instructions. learn to flash the Printrboard firmware at http://printrbot.com/support/instructions-and-guides/instructions-flashing-the-firmware-on-your-printrboard/ I used a normally closed button glued to the end of the probe, in series with the z end stop. If the probe is all the way in and flush with the aluminum extruder, the coordinates should be close to y = 0 x = 13 z = -10 so your input code should be something like M212 X13 Y0 Z-10 Into the custom gcode area in slic3r. make sure you do your own measurements, however. the z displacement is important! Brook's article explains a few things fairly well. http://printrbot.com/2014/01/19/printrbot-demonstrates-auto-bed-leveling/