Been meaning to make one of these for quite a while (along with MANY other things) but got some time this weekend to get this put together.
Sawhorse brackets, 2x10 seat and ramp, 2x4 arms and legs and some leftover 2x stock for the rest of the pieces. he pivot pin is a 1/2" aluminum bar inside a piece of PVC pipe strapped to the bottom of the bench.
Bench actually knocks down for easier transport. Legs come off, can take pins out of door hinges holding he ramp on and the pivot bar is removeable to take the arm off as well. T
Total cost, about $40 with most of that in the sawhorse brackets. Now I've got to make some bows with it.