Adjustable printer feet

Adjustable feet for the Prusa I3 (will probably fit other printers as well). Can be used if the printer is sitting on an uneven surface.

Needed parts:
* 4x M6x10 hex screws
* 4x M6 nuts
* 4x M5x10 socket screws
* 4x Drop-in M5 T-nuts (eg. [this](https://www.thingiverse.com/thing:2762571))
* 4x 20 mm felt pads (optional)

Installation:
1. Insert the M5 screw through the top part and attach it to the T-nut by screwing it in a few turns.
2. Insert the M6 nut into the top part.
3. Insert the M6 screw in the bottom part.
4. Attach the felt pad (optional).
5. Attach the top part to the aluminium profiles of the printer by screwing in the M5 screw.
6. Attach the bottom part to the top part.

Adjust the height of each foot by turning the bottom part. It fits a 16 mm wrench.

I've included the FreeCAD file in case someone would like to modify it.