NL HOME Power Lock Suction Cup Hooks Includes 4 Suction-Cup Hooks Each One With 20 lb Capacity Non-Suitable Materials Natural Timber Wood Veneer Sheets Cracked Tile Mosaic Tile Imitation Brick Tile Unsealed Marble Painted wall Wallpaper Concrete Wall Instructions – Step One: Wipe Clean and Wipe Dry the Surface Before Use Scrub the surface with a household cleaner, rinse and dry thoroughly. Clean the surface with rubbing alcohol and dry thoroughly. A suction cup will not adhere well to a dirty surface. – Step Two: Press the suction cup firmly in place, making sure there are no air bubbles between the cup and the mounting surface. – Step Three: Place where you want them, pull down hook & locks in place. Only Sticks On Smooth, Flat Surfaces (glass, mirrors, and tiles)