Cats scratch walls, furniture, and trees for two main purposes: one is to shed the dead outer sheath of their claws through the scratching action, exposing newly grown sharp claws; the other is to leave their scent by scratching to mark their territory and simultaneously send territorial signals to other cats.

　　The sweat glands on cats' paws secrete a scent, and when they scratch on furniture or walls, these scents remain. These familiar scents make cats feel safe at home and also inform other cats in the home: "This is my territory!" Cats that feel unsafe at home may scratch more often. Causes of insecurity might include the arrival of a new cat in the household or changes in the home environment (moving, rearranging furniture, buying new furniture, etc.). There may also be habitual factors; the author believes cats might like the feeling of scratching wallpaper. For a cat, digging their claws into wallpaper and watching small pieces fall off to become their toys may be very satisfying—the thicker the wallpaper, the greater their "achievement!" If a cat frequently scratches near the door, it might indicate they consider this a potential entrance for "intruders."

　　There are several methods to try to prevent cats from scratching walls. Prove to your cat that no other cats will enter the home to enhance their sense of security. You can place a doormat at the door; if you just came back from a friend's house with cats, wipe your feet at the door, quickly take off your clothes after entering, put away your bag, and change into clothes with familiar cat scents; use a soft towel to rub the sides of the cat's cheeks so the towel picks up their scent, then use this towel to rub the scratched areas. However, some habits are hard to eliminate, so it is recommended to repaint the walls slightly and, once the cat loses interest in the walls, replace the wallpaper.