Bondo® fiberglass resin is the same high-strength polyester resin that is used to build most boats. Can be used alone or with fiberglass tape, cloth or mat to repair damaged fiberglass boats, snowmobiles, jet skis, bathtubs and showers. Bondo® fiberglass resin can also be used as a sealer on damaged and rotted wood. It works to seal concrete, is great on large or small metal rust-outs and joins most surfaces together while creating a strong and long-lasting bond.