Use a rubber mallet to insert M6 bolt into this foot.
M6foot.FCStd is FreeCAD sourse. SHA 256 checksum:
ffb71c56107501f40c7906cf5b3915d82fb5f0aac231c8b7ef0cf4f1cb98c2a3 M6foot.stl
084dfc5bde08a2ef3df115b148ec0e5174a1ec464f34b58bcd21c086b5a931d5 M6foot.FCStd