The tool for fastening an elongated object (41) is of the tacker type and has a magazine (11). The magazine is designed for cooperation with a strip of U-shaped clips (17), each of which has its U-legs located one after the other, as counted in the longitudinal direction of the magazine. The clips are fed one by one up to a mounting station at the front end of the tool. At this station they are arrested by an abutment member (9, 37) in a well-defined, freely projecting position for mounting over the elongated object oriented transversely of the longitudinal direction of the magazine, by driving the fastening member (19) of the clips into the supporting surface with the aid of the driving element (3) of the tool. When driving the fastening element into the surface, the clip (17') located at the mounting station will be separated from the immediately succeeding clip (17).