This falls more to the portable and folding than benchrest- but is useful for other things.
What I have made is a 3/4 in plywood top about 16 by 40 inches. It has a cut out slot for a handle. The edges are rounded. It has two screw -n inserts which take a 1/4 -20 bolt. This goes on top of a steel folding sawhorse with legs of adjustable length. This sawhorse also has a handle. When the saw horse legs are adjusted to their maximum length they will fold- but are too long to go back flat. This is not a problem moving it around the range- but would not be convienent in a vehicle.
In use I put it at an an angle to the target. Shooting right handled this puts the front rest at the right side and the rear rest at the left edge.
As I indicated- it is not as rigid as would be ideal. I have not felt the need to do it- but rigidity would be significantly improved by running some paracord from each leg to the end corner of the table.
I have not done it yet but I am thinking about designing a bench which would use an assembly of unistrut for the legs. Unistrut is a C shaped channel used on most often in construction to hold pipes, conduit, etc. It is designed to be bolted together with connecting peices. It comes different guage metals, and a 1 1/8 and 1 5/8 rectangular or square sections. It would be possible to design a very rigid structure which could be quickly bolted together on site. If you wanted to spend a good bit more for lighter weight the same thing could be done with an aluminum, section called 80/20.
