Dear of troy: Sure, the post of a chair can be kept from coming apart by a swivel,
but everybody thinks about the chair turning.
And how about necks "swivelling"

I have been going nuts for past half hour
trying to remember the name of gadget that hitched plough behind my tractor.
A "C" shaped piece out of ultrastrong forged steel, with tips of "C" having 7/8? holes
through which a strong rod with strong flattened top, and a hole in tapered tip for
small chain to keep it from getting lost. The whole thing was called a clevis.