I also worked on the box, the sides are 1/2" plywood and the framing is 1"x1 1/2" lumber milled from 2x4's. So far the lumber has been free and the only costs have been the floor coating and hardware to mount the floor.
On the finished product, the box will detach from the frame. The NAT will store in my shop during the winter and it has to break down into components that will fit through my 36" wide shop door.
