What is a tie-off knot used for in sewing?

The tie-off knot in sewing is typically recognized as a method for tying off a thread in order to secure stitches, particularly when ending a stitching process. This knot prevents seams from unraveling and thus ensures the integrity of the stitching.

The first option describes a tie-off knot as a standard, modified seine knot for all stitches except the starting stitch. This option aligns with the practical application of a tie-off knot in sewing, where it is employed after a series of stitches have been made to secure them, effectively acting as a final anchor point. The specific mention of "all stitches except the starting stitch" indicates its use at the conclusion of stitch sequences, which is characteristic of its purpose.

While the other options may propose alternative uses or applications for knots within the sewing context, they do not accurately capture the primary function of a tie-off knot as effectively as the first option does. The use of a tie-off knot is fundamentally about securing stitches, and this is captured through the description offered in the correct choice.