Gender Reveal Party Yard Sign Letters - Boy or Girl Yard Cutout, Baby Shower Yard Decorations, Gender Reveal Yard Sign with Metal Stakes. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. These Boy or Girl Baby Shower Yard Letters full color direct printed graphics are vertically fluted for use with a Stakes. Coroplast is typically used for yard, parking, real estate, and election signs. They are waterproof.