Custom Dry Erase Yard Sign Personalized 24" x 18" - Coroplast Visible Text Custom Dry Erase Yard Sign with Metal H-Stake. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. These outdoor 24" x 18" Custom Dry Erase Sign for Business 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.