Why you should never practice with a wall hanger.
look through the above thread, and you can see how some of these are constructed.
More than one is taken apart.
Afterwards, it is pretty easy to understand why most people do not allow people to practice with these. There is a reason they are so cheap, and i certainly don't want to be around when someone is cutting, wether in the air, or trying to actually practice cutting with one.
Plus it makes it easy to understand why that one broke in the famous home shopping video.