QT, Ready To Use Floor Leveler, Latex Based Product Used To Fill Cracks, Fastener, Or Knot Holes & Level Low Areas In Plywood Subfloors Or Concrete Surfaces, The Floor Patch & Leveler Will Remain Flexible, Allowing Plywood Subfloor To Flex Without Cracking Through Filled In Areas, Ideal For Filling & Leveling Surfaces Prior To The Installation Of Carpeting, Vinyl Floor Tile Or Sheeting, As Well As Ceramic Or Mosaic Floor Tile.