It is an object to provide a fastening element (20) with less generation of jamming at the time of operation. Because a fastening element comprises a plurality of a unit fastening element arranged adjacently, the unit fastening element comprising a filament section (5), an inserting head section (19) equipped with a suitable engagement section located at one end of the filament section, and a socket section (8) equipped with a hole (10) for irreversibly passing the inserting head section (19) located at the other end of the filament section, the fastening element characterized in that a plurality of the socket sections (8) or their vicinities arranged adjacent to each other are temporarily fixed to the connection bar section individually installed, respectively, and a plurality of optional filament sections (11) adjacent to each other are separably fixed temporarily, jamming is less generated when the operator couples the fastening element by the coupler gun.