When mixing body filler I found it hard to find something that could be used as a mixing board and discarded without guilt or cost, but looking around the garage I could not identify something that fit the bill.
On the way to the parts house I noticed all the bandit signs and election signs posted along the road. I dislike these signs as visual pollution but recalled these are made from a plastic corrugated material that might be just what I need.
I pulled over and grabbed a few and cut them in quarter sections when I got home. They are just the ticket and I can use both sides before discarding.
If you are one of those people putting up those signs then I want to thank you for providing a solution to my problem.