The back portion is a box. But depending on how you look at it, it becomes one of those boxes that is impossible to close without crossing itself. Its an optical illusion, that I made out of pure luck! I showed it to someone and they were puzzled for a good 10 mins. I stood there saying its a box, whats not to get? See, its right there. The guy was like, I dont see a box, how is this a box? If you look at it just right, it looks like it has two cross braces supporting the front side at 45degrees.