This zipper was designed for the correct positioning of the zipper tape when sewing into the final product.
The contrasting line shows the distance needed for smooth slider movement on the zipper tape for its normal functioning.
If the product seam is located too close to the zipper coil, the slider will move by snaps, the fabric may be stuck in the zipper coil, which leads to damage of the zipper.
The stitch line is available on T6 and T6 reversed zippers.
