This penetrating co-polymer sealant is formulated to be so thin that by using capillary action it can find its way INSIDE fine cracks and set to a CLEAR flexible seal. Use for leaking windows, portlights, decks, coachroofs, deck houses, etc., cracked planks, centreboard casings, around all deck fittings, skin fittings, plumbing, trim - or any other fine leaks.