Abstract: Hollow closed-sectional elongate member is provided by bending a plastic strip widthwise. The closed-sectional elongate member has a crimped joint section provided on any one of its walls. The crimped joint section is formed by crimping together opposite longitudinal edge portions of the strip as the strip is bent widthwise. The crimped joint section extends along the length of the closed-sectional elongate member and thus functions as a rib reinforcing the rigidity of the elongate member. The closed-sectional elongate member is also curved along its longitudinal direction, to provide a closed-sectional curved elongate member.