Replaces butterfly nuts under the bed of CTC 3D Printers

These make level adjustments to the printing bed much easier and quicker.
4 of these are needed.

I found:
1) better results with ABS.
2) Print thumb wheel down
3) With supports. to make supports easier to remove I found that the following settings worked best:
....... Supports need to run across the face of the nut opening, not into the nut opening
...... Support to model Spacing 1.0mm
........Margin 0.5mm
........Density 0.25
4) Clean out the nut opening with a blade and the centre hole with a drill bit
5) Insert one of the "spare" nuts in the slot
6) Remove the thumbscrews evenly to avoid undue stress to the heater bed
7) Replace with new thumb screws