Parametric Stable Finely Adjustable z-Endstop

An adjustable endstop holder for either opto or mechanical endstops.
The endstop holder is static, as I found that most of the strategies for adjusting this introduced some wobble. The adjustment mechanism is attached to the X-carriage end using one of the screws which hold it together (or drilling a hole if you don't have any handily located screws).
The screw adjusts the height of the endstop flag using my 'decimal' thumbscrew - (originally from my bed levelling kit - http://www.thingiver