Bed Cover?

[vht]

I'll have a tool box in the front that sits in the bed for straps and such. I'm thinking about building something for the rear of the bed that I can lock and take out easy, then put a soft type cover over it. Found 1 on ebay, alum frame, all comes out easy, plus just the back part will open if you want. If somebody is going to steal something, they're going to get it. I just want protection from weather and not have something that sticks out like a sore thumb.