There is a guy at the rifle range who uses those stands for road works (you know, the board/signs wedged with the two legs on an angle ?)
He made up a three (6 if you count the feet of each leg) legged bench, that is so stable and rigid, it's not funny.
Then there's the guy on Shooters' Online who decked out the back of a Chevvy van as a shooting bench/reloading lab etc. That rig (had caravan screws each corner) was a very nice piece of kit.