It’s a dismountable snap fit. The holding force is relatively low (depending on the hook width). The knob is the protruding middle part between two holes. If the two parts are snapped together, they can be twisted a bit like a hinge. By designing a smaller neck for the knob (or extending the cylindrical shape without neck), its rotation angle can be increased. The f3d-file has some more parameters. Tested with PETG and PLA.