How to fix it depends on the wall of the site: if it is smooth tiles, flat painted walls. You can use a transparent suction basin, tie the two together with a thread, and use the suction of the suction basin to suck on the wall. If the ordinary wall is fixed with transparent tape, you can also fix the line on the wall with a small pin. The former is harmless to the wall and easy to clean. The latter has certain damage to the wall.