Of course there are some screws, bolts, and even a little plastic on the casters, but the primary input is WOOD, solid wood, hardwood. No plywood, no veneers, no chipboard. Wood, real wood. Right now, we are using birch. Birch is not a long lived tree. As a result, harvesting older birch is ideal. We are considering switching to beech because of the die off that is so troubling but puts a bunch of supply on the market.