Optionally, the hook structure 2 may further include a reinforcing rib 23. The reinforcing rib 23 is arranged on a side of the body portion 21 away from the hook portion 22, and an end of the reinforcing rib 23 is connected to a sidewall of the body portion 21. In the X direction, a size of the reinforcing rib 23 is smaller than the size of the body portion 21. In the Z direction, a size of the reinforcing rib 23 is equal to a size of a combination of the hook portion 22 and the body portion 21, that is, a top surface of the reinforcing rib 23 away from the positioning bottom 16 is flush with a top surface of the hook portion 22 away from the positioning bottom 16. By arranging the reinforcing rib 23, a strength of the hook structure 2 may be increased, so that a matching between the hook structure 2 and the slot 524 may be more firm.

For example, the body portion 21, the hook portion 22 and the reinforcing rib 23 included in the hook structure 2 may be integrally formed.

Optionally, the rear cover 1 may further include a first set of supporting ribs between the second concave sidewall 1522 and a receiving portion 18 and a second set of supporting ribs between the third concave sidewall 1523 and the other receiving portion 18. For example, each of the first set of supporting ribs and the second set of supporting ribs may include a plurality of supporting ribs 19. The plurality of supporting ribs 19 are arranged at intervals in the Y direction.