Off Topic 2,
I have watched the self propelled variety, Staging ( those big scaffolding towers on wheels about 70 foot high manually pushed around ) used to work on the DC9 tailplane, caught by the wind it trundled off on its own, luckily no one was hurt, one fell over, another managed to park itself deep into a Civi Hercs nose and another used a BAe 125 belonging to a famous digger company as a chock.