I made a shelf for hiding all the crap at the bottom of my truck (jack, tools, tire shine, stuff like that) and for keeping the stuff I use a lot on top so I don't have to go fishing in the bottom of the trunk for it. Simple enough, just cut a piece of particle board that I had lying around in the shape of the top "level" of the trunk, ran to JoAnne fabric's and picked up some headliner material, stopped at the auto parts store and picked up some 3M spray on headliner adhesive, just the fabric to the right size, sprayed the board, and stuck the fabric on.