Bringing groceries home from the store, I hate how things roll around, bruising produce and risking breakage of glass items. I've seen bag-holder hooks on pricier vehicles, and nifty cargo nets for many others. I didn't really need something large, and figured that something even just a few inches high would hold most things towards the "front" of the trunk. A board across the wheel wells, with velcro at the ends to hold it in place, would probably be enough.
(In the picture, you can also see a right angle of wood, which has velcro on the bottom. This is good for holding individual items in place, and is actually an imitation of something I saw in a catalog. It works well for boxes and suitcases, but not so good for multiple bags of groceries.)
When I need to use the full trunk, I can just lat the board flat on the floor of the trunk, and it is out of the way.
Additionally, the project used some "Tacky Glue" craft glue, and a few staples from the staple gun.
I decided that sewing was going to be overkill for this particular project, and used glue almost exclusively. After measuring the width of the truck just aft of the wheel wells, and cutting the board to length, I smeared glue all over the board and stuck the fabric down. I weighted board with bricks to keep everything flat while the glue dried. I folded the fabric over at the edges and ends to keep it from fraying. Really, it was quite like wrapping a package.
To keep the divider upright, I wrapped Velcro strip around end end, gluing it into place all the way around and stapling the ends down to keep it from peeling off over time. The Velcro is visible in the photos above. Though it looks sort of like a "cap" on each end, the Velcro doesn't actually go over each end, just around each end like a cuff.