Colido/Print-rite Bed Leveling guage

after sniffing about for a bed leveling gauge design for my printer (the manufacturer supplied calibration technique is erm.....less than exacting to say the least) I couldn't find any I was happy with, some were just not usable, others were simply over engineered for purpose so I designed and made my own using the same "digital tyre gauge" that seem popular with other similar designs.

gauge is good for 1/100th of a millimeter and works very well with my design, has my bed printing bottom la