To reduce a work man hour, shorten a making term and also install a coupler socket accurately and surely by installing at least two or more coupler sockets to a doubler at a constant interval and fixing weldingly the panel to a hull after making to the panel.

At first, plural coupler sockets 1 are installed per a length A on the doubler 2 which is a long band plate. The installation method is not limited especially but the end of the coupler socket 1 is installed on the prescribed position 5 of the doubler 2 by welding. The welded place 3 is formed by the circumferential outer edge of the coupler socket 1 and the structure connected to the upper surface of the doubler. Then, the plural doublers 2 are made to a panel by installing to a temporary reinforcement material. After installing the panel, individual doubler is fixed weldingly. Thereby, the mutual interval of respective doublers is made to a prescribed interval B. Meantime, it is favorable from the view point of a work efficiency that the welded places 4 are provided discontinuously at the prescribed interval.