Katrina Christiansen US Senate 2022 Yard Sign - Coroplast US Senate Election North Dakota 2022 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 Katrina Christiansen US Senate 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.