Larry, on the new unit Coats sells:
http://www.ammcoats.com/coats-manual...nger-model-310
the bar just bears against the side of the center post...the threads
are very course acme, and above that no threads, just a solid bar. In
any case the rectangular hole in the top swivel of my unit is about
1/2" wide x about 2" high...kinda small for a substantial bar to go
through. Maybe the bar had a spigot on one side that fit in the hole
but I'm just guessing.