When I go camping I'm sick of having to unload to get to stuff on the bottom, so I decided to build a shelf. Since it was going to be large and flat anyways I figured I might as well give it four legs in case I have a need for a "table" while camping. It's a little short so it's not ideal, but better than the ground I suppose.
Hardware to hold the legs on. 1 bolt, washer and nut coupler (heheh) for each leg.
Table legs 2 x 2 x 15
Shelf/Table top 43 x 32 1/2 x 1/2 (I used birch because it's what they had precut to 4x4 for easy transport)
I drilled a hole slightly smaller than the nut coupler in the rough center of each of the legs, I wish I had a drill press.. then I used some construction adhesive and pounded the nut couplers into the legs.
Hardware in place
In table form
In shelf form, I used a piece of 1/2 x 4ft round steel which slides into the latches for the third row seats. This gives enough room to fit the footlocker underneath the shelf without interference.
In the future I plan to put some type of grating so that items on the top can't slide forward. And I still need to figure out how to attach the wood to the steel crossbar.