On Jan 3, 9:21 am, steamer wrote:
--I never did get the wall thickness. It *is* 'tube', yes?

He's tapping the ends of 80/20 extrusion, so they have a small hole in
the center of the extrusion shape. http://www.8020.net/ right in the
middle of the photo on the front page of their catalog, you'll see two
side views and the end view.