Old Masters? Exterior oil-based spar marine varnish is a durable exterior coating. This product can be used on wood, fiberglass, coated metal or painted surfaces. It contains ultra-violet absorbers for advanced sun protection. Use on exterior surfaces such as fences, railings, lawn furniture, doors, boats and marine surfaces. For interior use on windowsills and door frames for added ultra-violet protection. Do not use on wooden decks or steps, wood siding, log homes or wood boats below waterline. As with all exterior clear finishes, this product will not offer unlimited protection against the elements. Surfaces which receive direct sunlight may have to be recoated annually to maintain gloss and to prevent cracking and peeling.