The second outlet 72 of the first channel portion 61 is provided in a central region in the front-back direction of the first case body 10 (frame member 11). The second portion 612 is connected to a space portion 613 formed in the first case body 10 (frame member 11). The space portion 613 is connected to the second outlet 72 (see FIGS. 6 to 8 and the like). In other words, the first channel portion 61 of the present embodiment is constituted by the first portion 611, second portion 612, and the space portion 613. Specifically, the channel 60 may include a portion that is not long and narrow as a groove, as long as it is a region through which water can flow (may include a sizable region such as the space 613). The first portion 611 and the second portion 612 are grooves that are open upward, and the third case body 30 is provided so as to cover these openings. The space portion 613 is a portion that is covered by the second case body 20.

As described above, the space portion 613 is connected to the second outlet 72. In the present embodiment, a hole (space) that serves as the second outlet 72 is formed in the second case body 20. Specifically, a portion of a slit 211 formed in the second case body 20 functions as the second outlet 72. In other words, a slit 211 that is formed for enabling deformation (cantilevering) of the lock piece portion 212 is used as the second outlet 72 for drainage (see FIG. 6 and the like). In this way, the second case body 20 is provided with a portion that serves as the second outlet 72.