Tailor Tack Foot #7 (0025827200) is great for marking seam lines. It can also sew elegant decorations, imitation hemstitch, fringe, and 3D effects.
When sewing two pieces of fabric with Tailor Tack Foot #7, loosen the thread tension a bit. This helps the thread pass easily over the ridge in the center of the foot. The zigzag stitch used forms loose loops which then slide off to the back thanks to the special V-shaped opening on the foot.
For marking seam lines or darts, someone carefully pulls the fabric apart after sewing. You can also use the Tailor Tack Foot #7 for decorative purposes.