A sealer is a type of product used to protect wood from damage caused by moisture or chemical reactions. Various types of sealers are available on the market, such as stains, shellac, paint, and oil. The primary function of sealers is to block the pores of the wood to protect it from potential harm. Sanding sealer is a popular type of sealer that is applied thinly to provide a smooth surface for subsequent coats of finish. Some sealers create a barrier around the surface of the wood to prevent damage caused by cleaning products. Others prevent the grain from rising or add color and depth to the wood. The term “sealer” may also refer to a type of finish applied to the wood.