Herringbone Stitch (Sewing)

Intermediate Finishing

A crossed, X-patterned stitch worked over a hem or seam allowance, giving a decorative finish with some built-in stretch.

Fold the hem up to where you want it and work from left to right, with the needle pointing back toward the left, similar to catch stitch.
Bring the needle up through the hem allowance just below the fold.
Take a small stitch in the main fabric a short distance up and to the right, catching only a thread or two.
Take a small stitch in the hem allowance a short distance further up and to the right of that.
Continue alternating between main fabric and hem allowance, always moving up and to the right, so the stitches cross into a series of X shapes along the hem.

Herringbone stitch is essentially a wider, more decorative cousin of catch stitch — the mechanics are the same, just with larger, more visible crosses.
The crossed structure gives this stitch noticeable stretch, which is why it's often chosen for hems on knits or bias-cut fabric that need to move.
Because the stitches are meant to be more visible than an ordinary hem stitch, herringbone is sometimes worked in a contrasting or decorative thread on the outside of a garment.