Abstract: An attachment for supplying a filler wire to an electric soldering iron of the pen type includes an independent support butt having an upper housing provided with a V-shaped groove defined by two lateral faces of a dihedron. The cylindrical body portion of a pen type soldering iron is received in the groove and fixed therein by a flexible, length adjustable clamp passing around the body and having its ends fastened to the butt so as to maintain the body tangentially to the faces of the dihedron so that it forms a unit with the butt. The adjustable clamp permits soldering irons whose bodies are of different diameters to be immobilized in the groove. The support butt is provided with a manually operable trigger actuated mechanism for incrementally feeding and guiding a length of filler wire toward the heated tip of the supported soldering iron during use. The power supply lead for the electric heating element of the electric soldering iron extends through a passage in the support butt.