This presser foot is use to sew overcasting in order to prevent the cut edges of fabric from fraying.
Sew with the edges of the fabric aligned with the guide. The prong in the opening of the presser foot presses down the edge of the fabric to prevent puckering. In addition, the amount of thread going into the stitching is adjusted by the thread crossing the prong, creating clean finish with little shrinkage.
This presser foot cannot be used to sew zigzag stitches or overcasting by 3-point zigzag.