Undercoating is a process of applying a protective coating to the underside of a vehicle. It is typically made of rubberized or sound-deadening material and is applied to protect the vehicle from rust, corrosion, and other damage. The SEALER is a type of undercoating that is used to provide an extra layer of protection against water, dirt, and other elements. It is usually applied after the undercoating has been applied and helps to keep the undercoating in place.