Personalized Senior Graduation 2023 Yard Sign - Coroplast Grad Sign, Class Of 2023 Seniors 23 Sign, Graduation 2023 Yard Sign with Metal H-Stake. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. This Custom Graduation 2023 Yard Sign full color direct printed graphics are vertically fluted for use with an H-Stake. Coroplast is used for yard, parking, real estate, and election signs. They are waterproof.