50 or 60 years ago, my grandparents traveled around the country in their car from their home in MO. They would come to see us. visit other family members, and, as early snowbirds, to the southwest.
In that era of few rest stops and picnic tables, Grandpa made a folding table that hooked over the trunk opening. That and a could of folding chairs and they had a place to eat, and a trunk to have the picnic basket handy.
My grandfathers and father (my threefathers...) are where I get my skills from.)
So, I keep tools and parts and such in the trunk of our 31' Sunstar. After a few trips, I got tired of setting a tote or toolbox on the ground to look for something. Then I remembered the trunk table. The details are hazy, but I had enough of an idea of what I wanted to make.
The table is a scrap of 3/4" MDO. The legs are 2x2s. The "front" edge hooks over the bumper with a piece of aluminum angle. I had everything except the folding leg brackets on hand. I ordered those on-line. Fate and my threefathers smiled on me as the width of the MDO was exactly the inside dimension of the distance between 2 bumper bolts.
The dimensions were all by inspection, to fit that space. The legs are the same length as the height of the bumper. The length of the legs folded up determined the length of the table, plus a little extra so they would fit inside the angle when folded.
I had to rip some extra 2x2 in half and glue and screw it to the tops of the legs to make them wide enough for the hinge brackets.
Here it is folded up:
Here it is installed:
The legs really are plumb. The apparent slope is a trick of camera perspective.
It would be easy to make a similar table to fit in any storage compartment opening. I bought 2 extra leg brackets just in case I decide to do so.
And, it's strong enough to hold my 220 lbs.