I needed to be able to lock up my gear so I designed a three-panel lid and had it built out of diamond plate aluminum.

Front and rear sections hinge on stainless piano hinges and lock. Center section is bolted flush to the top of the bed rails. A vertical bulkhead behind the front seats completes the package. Minimal drilling to install. It's a beautiful thing. The edges of each section are c-folded for structural integrity. You can stand on it without flexing it. I've used it often as a shooting platform with a large-format camera.