There must be air in it, and the sucker can't form a vacuum state, so the hook naturally falls down. Pay attention to these aspects: 1, it is best to use ceramic tiles, glass and stainless steel on the wall, which is easy to form a vacuum; 2. The sucker should not be damaged. 3. Clean the wall with a soft cloth before sucking, preferably with a warm and wet cloth, and then dry it. When inhaling, you must try to squeeze out the air. 4. If the sucker is not only complete, you can put the sucker into a bowl and pour boiling water. After a period of time, the sucker will naturally recover.