Similarly, although the second guide pins 68 are provided to the second main wall 56 and the second guide holes 34 are formed in the end wall 32, the second guide pins 68 may be provided to the end wall 32 and the second guide holes 34 may be formed in the second main wall 56.

(5) As illustrated in FIG. 15, the first positioning pins 81 are provided to the first positioning panel 72 and the first positioning holes 22 are formed in the first fixing portion 21. However, the first positioning pins 81 may be provided to the first fixing portion 21 and the first positioning holes 22 may be formed in the first positioning panel 72.

Similarly, although the second positioning pins 101 are provided to the second positioning panel 92 and the second positioning holes 26 are formed in the second fixing portion 25, the second positioning pins 101 may be provided to the second fixing portion 25 and the second positioning holes 26 may be formed in the second positioning panel 92.

(6) As in the following first to third modified examples, the cable unit 50 illustrated in FIG. 5, etc., may include sliding mechanisms 120 that support the second casing body 53 so as to be slidable relative to the first casing body 52 along the direction in which the first main wall 54 and the second main wall 56 face each other.