On the second garnish 2 near the rear end thereof (to be butt-joined with the first garnish 1) is formed a male engageable protrusion 19 that protrudes toward the first garnish 1 (in the direction of the width of the vehicle in the present embodiment) and extends vertically at the inner surface of the side plate 10 b as shown in FIGS. 2, 8, and other drawings.