Rendered in detail from the illustration.
The back has two snap closures made to fit through holes punched in the belt. They will be a bit stiff at first but work them a few times and they'll be smoother. I have made this model a couple times and I would have to work pretty hard to break any part of it.
The back has been hollowed out to save 5 or 6 bucks on materials.
I added a slight curve for ergonomic purposes which may not be immediatly obvious in the renders.