It loiks like it clamps into something. I don't see a way to hold it behind a dent while hammering on the other side with the appropriate size body dent hammer. Here's my dent dolly:
I think mick56 is spot on. These things come in a verity of shapes and sizes to allow you to get in tight spots and conform to certain shapes.:thumbup:
It is evidently a common body and finder dolly that comes in a kit. The one that I have was a common stand alone hand dolly that was easily purchased at auto stores back in the olden days.