I've got this black 2020 extrusion which does not have a round hole, but is partially round and partially square. Tapping is possible, but it's a bit uncomfortable. So I designed this little add-on for a tapping tool which allows to create a perfect and square thread for a M6 screw. Of course the little tool also helps if the extrusion has a round hole.

What you need: M6 nut & screw, M4 nut & screw (if you want to make use of the fixation screw), 7g of filament