Happy Mother's Day Yard Sign Letters - Happy Mother's Day Yard Cutouts Lawn Decorations for Mother's Day Party Yard Signs with Metal Stakes. Economical and durable, our Coroplast Yard Signs are a staple of outdoor advertising. These outdoor I Love You Mom Outdoor Lawn Letters Decorations Yard Signs 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.