If your cat has urine-marked on an indoor surface, use the following easy procedure to help eliminate cat's impulse to remark. Works great on indoor plants and Christmas trees too! For outdoor plants, use Pet Stopper by Pet Organics. Shake well before using. Clean affected surfaces with alcohol or water only. When the surfaces dry, mist-spray NO MARK on affected surfaces twice daily for one week. Then once daily, as needed. If urine-marking should re-occur, just repeat the above procedure.