To prevent the generation of a recession on the bottom surface of a flange part and to produce an arranged application portion at high productivity by locating an injection port to a thermoplastic polymer application portion in an end surface in the arrangement direction of the application piece of the flange part.

In a thermoplastic polymer application portion, lots of slender, flat application pieces 10 are separated from each other and arranged in a line, application lines 11 in which one end of each piece 10 is continuously formed to make a base part 8 are laminated so that the pieces 10 are in the shape of a cross-stitch, and both end of the base part 8 of laminated application lines 10 are continuously contacted to form a flange part 9. In addition, in the application portion the position of the molten resin injection port 13 during injection molding is made the end surface in the arrangement direction of the application pieces 10 of the flange part 9. By this, since a recession is apt to occur near the injection port 13, by making the port 13 the upper end part of the flange part 9 which is remotest from the bottom surface of flange part 9, the generation of the recession can be prevented, enabling the production of the arranged application portion at high productivity.