Happy Labor Day 2023 Yard Sign - Coroplast American Labor Day Sign US Flag Stars & Stripes Patriotic Happy Labor Day Yard Sign with Metal H-Stake. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. These outdoor Happy Labor Day 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.