Customisable alignment tool for MPCNC build

This is some tool I made to help me adjust the height and positions of the corners in [my MPCNC build](https://www.thingiverse.com/make:550166). You will need four of those tools, one for each corner.

BOM:
- four parts of the tool, times 4 for each corner
- M8 screw with hex head and of required length according to height of your build
- 2 M8 nuts
- 1 M8 washer
(change scad file if you prefer different screw types)

To assemble the tool:
- print all four parts of the tool
- push the screw down into the top_foot part, so the screw head sits completely in the recess
- push fit the top_head into the top_foot part, should fit nicely while holding well
- screw nut and washer onto screw (those are for securing the knob into position)
- put knob part onto screw so that its opening faces away of the head
- screw remaining nut onto screw and use the securing nut to pull the outer nut firmly into the recess within the knob part
- put all this assembly onto the foot
- adjust