I don’t besmirch the fellow who built the bench, but the topsheets should be rounded on the edges and the bases mounted downwards and/or away from the person sitting in the chair, not because the edges are sharp (which I hope they aren’t) but because they are high-carbon steel and rust insanely quick with any moisture so you’ll get a nasty big rust stain on your clothes or skin if this thing gets wet.

One time I used some worn-out skis as latitudinal leaf springs for a bedframe. That was fun, very bouncy.