Left over Campaign Signs Answered

If you're looking at the type I'm thinking of, the material is called Coroplast (corrugated plastic). 
Googling around a bit I've found people using it for bike fairings, pet containers, model aeroplanes and storage boxes.
With a bit of ingenuity, you could probably laminate several sheets together and build furniture out of it.

My son's Scout troop went out once and collected all of the left behind campaign signs to haul to the dump. Before hauling them off, however, they removed most of the lath stakes and posts used to hold up the signs and used the wood for numerous Scouting projects afterwards. I know because they stored most of it in my construction yard.

What are the signs made out of?

Furniture?

Lumber?

winter heat. How ironic, considering all the hot air that the politicos revel in.