Some are put back to back and put up in a cantilevered style on metal cylinders beside well-traveled roadways. I am now looking into what sort of sized are used. The one I worked on was rather old, last painted in 1994. It was without the frame 10'6" high, and 44' wide. It had 22 panels 2 feet wide that slid down onto a metal frame. And a patent stamped onto it.
Some are now 14 feet high and 48 feet wide.