I've hung a lot of iron in my day and I have never seen anything like that, BUT, it is a very good idea, if the spindle was threaded so your hands were not tied up I could see that as being a good tool for levelling single a storey structures. It's fairly common practices on single story pre enginered buildings to use a 4' or 8' level to plumb the structure but if the stucture is multi story the old method was plumb bobs but these days the norm is to use a transit or now referred to as a total station. Be interested to here what others have to say.