I've worked on a number of election campaigns and there is sometimes the post-election issue of what to do with election signs. Often a candidate will keep them for another election but, for assorted reasons, they might not be needed or wanted.
On a couple of occasions I was contacted by high school drama teachers. Turns out the corrugated plastic is ideal for building sets. Lightweight, paintable and easy to store for reuse.
I found the above ingenious use of election signs in the yard of a house off of Bannatyne Avenue. A combination housing material and electoral history lesson ! I'll have to stop sometime and ask the guy how they hold up to the elements !