"Remember when billboards were near the ground?"

"No"

"Sure you do. The cops used to hide behind them in cartoons."

"Ohhhh, yeah... I do remember that"

No because I'm not old.

I got to go on tour of a place that made them back in the early 70's.  The billboards were built in sections that could be disassembled and moved to different locations. 

The blank white billboards would have slide images projected onto them in a warehouse.  The artist would then mark the outlines with an electric pencil, working from a scaffold.  After outlining, the artist would hand paint the features in while looking at a print that a different artist had designed.  Definitely a lost art.

back in the 50's i stashed my DeLorean behind one: