I think we used 3 boxes of shelving for it. The third column of squares from the left is the door which opens all the way from top to bottom. It is connected with cable ties on one side and then we have some little hooks (like at the end of a dog leash) holding closed the other side. This way we just unhook the door and open it and he can come out and hop around (after we secure the doggy door of course!) and go back in as he pleases. The "shelf" that the plastic container is on is just squares, cable tied together, and then wooden dowels supporting them so they don't bend under the weight. Wooden dowels also hold up the small shelf on the right, which is a real shelf wrapped in a towel, with one end of the towel left draped over the side so he has a privacy area. He loves to chew on the towel and especially the dowels underneath it. We replace those every few months. I'd put in PVC, but he really likes to chew them and it makes him happy. Dowels aren't that expensive!
Now it is time to go work the bunny berries and the kitchen scraps into the next few squares of my garden to prepare for fall. Slowly all of the squares are being emptied of crops and can rest until the fall planting, but they sure look empty and lonely. I'm thinking of trying to plant some lettuce under shade cloth and see how it does. Since I can't plant much of anything else, if it doesn't work I'm only out a few seeds. Whereas if it does work, I have fresh lettuce this summer!!! :)