Royal Paints is a brand of paint that likely offers an undercoat product as part of their line of paints. An undercoat is a type of paint that is applied to a surface before the final coat of paint. It is typically used to provide a smooth and even surface for the final coat of paint to adhere to, and can also help to hide imperfections in the surface. Undercoats are commonly used in both interior and exterior painting projects, and may be made from a variety of different materials depending on the specific product and intended use.