It is after all a simple ball and socket joint; it has certain loads imposed on it; it needs reliability over a defined life; it must contain materials suitable for the working environment.

It's much harder, they say, to dislocate a screw than a round-ball-and-socket joint.

They made joints in stone keeping the lintels in place horizontally using a tongue and groove joint and subsequently fixing the upright and lintel with a ball and socket joint or mortice and tenon.