Cats scratch walls, furniture, and trees for two reasons: one is to shed the dead outer layer of their nails through the scratching motion, revealing the newly grown sharp nails; the other is to leave their own scent through scratching, indicating that this is their territory, and also sending territorial messages to other cats.

　　The sweat glands on cats' paws secrete a scent that is left on furniture or walls as they scratch. These familiar scents help cats feel safe at home and also tell other cats in the house: "This is my turf!" Cats that feel unsafe at home may scratch more frequently. Causes of insecurity may be due to a new cat arriving at home or changes in the home environment (moving, rearranging furniture, buying new furniture, etc.). Habit may also play a role; the author believes cats might like the feeling of scratching wallpaper. For a cat, digging its claws into wallpaper and watching small pieces fall off to become their toys can be a very satisfying achievement; the thicker the wallpaper, the more pronounced their "achievement"! If a cat often scratches near the door, it might indicate they consider potential "intruders" to enter from there.

　　There are several methods to try to stop cats from scratching on walls. Prove to the cat that no other cats will enter the home, which can enhance their sense of security. You can place a doormat at the door; if you just returned from a friend's house with cats, wipe your feet at the door, quickly remove your clothes upon entering, put away your bags, and change into clothes with familiar cat scents worn at home. Use a soft towel to rub the sides of the cat’s cheeks so that the towel picks up the cat's scent, then use this towel to rub the scratched areas. However, some habits are difficult to eliminate, so it is recommended to lightly repaint the wall. After the cat loses interest in the wall, you can replace it with wallpaper.