Corrugated plastic signs make great lightweight roofing for my rabbit and chicken pens. I lay them like shingles and attach with wire.

I think they contain UV protectant, but probably could be painted also. Many of my pens are wire clipped together without a wood frame, so a lightweight roof is perfect.

There are local elections this weekend, so I expect to be able to get more out of people's trash. Some places, the city will seize/pull illegally-placed signs, and you can get them from the appropriate city dept.

I do not advocate stealing signs - always find out if you can take them, ask the city/county or sign owner, take them from trash, etc.