The tube itself is very thick and sturdy. I use a razor blade - DO THIS WITH THE UTMOST OF CAUTION, or use a carton cutter if you have one. It has a little more protection when holding it. After cutting the length I need (which is the length of the hanger bottom minus 1"), I slice through the length of the cardboard so I can "open" up the tube and slip it onto the hanger bottom. I then cover the tube with batting and secure it in place with a piece of tape at the ends and middle.
The great thing about this hanging system is that the fabric sticks to it, like it would to a flannel board. And because it's tubular, there's no crease in the fabric where it would normally bend over the wire.