not pictured: i also cut a 1/2" plywood bottom for inside so the bolts have something firm to anchor in. there will also be a plywood back wall for the struts, and i'm thinking of maybe covering the other walls with thinner plywood sheets maybe just for the hell of it?
oh the metal is all salvaged scrap. the I beam was something me and my dad found buried in the brush at this house like a year or two ago, and i think the previous owners had used it to build a trellis for the muscadine that was taking over the back yard.
not sure where the square tubing came from, but it was in the same scrap pile.