An elongated jointing device in the shape of beam body has a substantially H-shape in cross section, the lateral bar portion connecting the pair of parallel vertical portions of the H configuration serving as a distributed fulcrum. A pair of flanged members are positioned with the contact surfaces of their flanges being mated. One of the grooves of the jointing device is fitted onto the mated flanges and pinches them. By inserting at least one wedge into the other groove of the device, the one groove is narrowed thereby pinching the mated flanges and an intimate joint is formed between the two members.