For those that have found some dificulties to find M3 square nut, download and print this adapter, that fit perfectly in Graber lasercut frame. Available in normal nut and nyloc nut version.

Print Profile:

Infill - 100% rectlinear
Perimeters - 2
Perimeter speed - 15mm/s
Infill speed - 30mm/s
Extrusion width - 0.40mm (or less, not less than nozzle)

Print 4 or more units at once, or use cooler.