Reverse Bear Trap
I don't understand how Hoffman got out of it. I mean, wedging it between the bars on the doors was ingenious, however surely there was no way to actually remove it off his head? Going by the induced injury (sliced cheek due to the stick of metal in his mouth), Hoffman basically slid out sideways of the contraption. That's not possible.
And anyway, escaping how he did, the fact that that piece of metal had blunt edges, it would have removed the flesh from his jaws before it sliced through the cheek. That would have been a much better spectacle!