Ruscoe #1 Gutter Sealant is Recommended for sealing openings less than 1/8”. Can be used as an effective sealant against water, chemicals, air and dirt for sealing seams in gutters, downspouts, roof and chimney flashings, troughs, wood, concrete, ceramic, brick, metal, stone, masonry, marble and glass. Recommended for sealing horizontal and lap seams only.