Well, I know I should have a pickup if I'm going to be a "real woodworker" but that isn't in the cards.
So when I have to lug big sheets of ply or a load of lumber I use this temporary rack I made out of 2x4s.Attachment 5161
There are two "C" brackets on each board, construction adhesive and drywall screws the "C" faces forward and the roof rack bar is captured by another block of wood secured with a drywall screw through the 2x4 into the bottom part of the "C"Attachment 5162
Then I load it up and secure with a bunch of clamps.
Don't drive more than 45 mph with this rig, but it gets the stuff home and I don't get TOO many funny looks