The 15 and 17 series use the Supplemental Thread Carrier to add a decorative thread to the edge of the stitch. The Supplemental Thread Carrier is also used by the FJ and FJT Series to add a decorative thread and to help control the stitch. The 15 and 17 series machines can work without the Supplemental Thread Carrier, the FJ and FJT Series require it to make the stitch. In either case the Supplemental Thread Carrier can be installed and not threaded.

The Supplemental Thread Carrier moves back and forth over the Presser Foot, to carry the extra thread into the throat of the Hook.

The Supplemental Thread Carrier should be adjusted a low as possible, but should always clear the Hook. The Supplemental Thread Carrier is adjustable vertically, and can be rotated by loosening the Screw at the left hand end of the Rocker Shaft.

It can be adjusted forward and backward by loosening the Clamp Screw on the upper end of the Cam Lever on the Rocker Shaft.

On the FJ and FJT Series Machine the Supplemental Thread Carrier carries the Needle thread forward on the outstroke of the Hook. The Needle thread slips off the Supplemental Thread Carrier at its farthest forward position. The Needle thread is then forced back into the Hook by the rearward stroke of the Supplemental Thread Carrier.