BARS #1: FOR NEIL COCKERLINE: ABOUT HORIZONTAL BARS

As far as I know, all Horizontal Bars were made of Hickory, probably for it's strength, & flexibility,
the same reason it was used for tool handles, shovels, rakes, & hoes in particular.
Thus the terms, "Hoe Handlers", & "Hickory Stick Artists", applied to "Bar Actors"

Years ago when "Craftsmen", were plentiful it was easy to get bars, Blondie LaBlonde said they got them from a man in Oregon, and if they weren't pure white they would send them back. The difficult part of making bars is that it was necessary to drill a 5/8" hole lengthwise, through the center and insert a steel core up to 6ft long for added strength, if the drill bit started following the grain it would come out the side, and that bar scrapped. About 6" of each end of the bar was left square so it could be put in a socket to keep it from turning, the socket also had the connections for guy lines, in the old days these were made of brass. The core was threaded on the ends to keep it in the socket.
I have heard of people using bars without a core, but I also heard of them breaking, if a bar "cracked" length-wise while you were on it some serious damage to the palms of the hands could result.
Years ago a cracked bar would be discarded, as they became harder to get we would repair them by wrapping fine wire around the cracked area, and cover that with non-waterproof adhesive tape that was not slippery. In later years Johnny Hartzel made his own bars, and a man in Cleveland experimented making two halves, grooving them out, & gluing them on each side of a steel rod, they weren't overly popular.
The only act I ever saw use Steel bars was The Three Merkys(sp?), and they wrapped them with a very fine twine.