Gretchen Whitmer For Michigan 2022 Governor Yard Sign - Coroplast 2022 Gubernatorial Elections Michigan Race Red White & Blue Yard Sign with Metal H-Stake. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. These outdoor Gretchen Whitmer Michigan Governor Yard Sign full color direct printed graphics are vertically fluted for use with an H-Stake. Coroplast is typically used for yard, parking, real estate, and election signs. They are waterproof.