Valentines Day Yard Sign Letters - Heart Arrow, Cupid Yard Decorations for Happy Valentine's Day Party Outdoor Yard Décor With Metal Stakes. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. This outdoor Love Yard Letters Heart Yard Sign Happy Valentine's Day Yard Sign with Stakes 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.