A stretch stitch is a stitch that returns to its original length after being stretched, rather than simply having slack in it.
A straight stitch has no give at all: stretch the seam and the thread reaches its limit and snaps. This is why a straight-stitched T-shirt shoulder pops the first time it goes over someone’s head.
A zigzag has give because the thread travels a longer path than the seam line, so stretching the seam straightens the zigzag rather than loading the thread. That works, and it is what most people use.
A dedicated stretch stitch — usually marked with a lightning bolt, sometimes called a lightning stitch — goes further: it is designed to recover, so the seam returns to shape rather than staying stretched.
Where to use it. Any seam on a knit that will be stretched in wear: shoulders, side seams, cuffs, necklines, waistbands.
Where not to. Wovens, where it adds nothing and is harder to unpick. And anywhere you need to remove the stitching later, because a stretch stitch is dense and unpicking it is slow.
If your machine has neither a stretch stitch nor a satisfactory zigzag, a narrow zigzag at 0.5 mm width and 2.5 mm length is the practical fallback and it holds well.
Questions people actually ask
My machine does not have a stretch stitch.
Use a narrow zigzag — around 0.5 to 1 mm wide, 2.5 mm long. It is very close in practice and it is what most people used before the stitch existed.
Should I use it for hems on knits?
A twin needle gives a better result on hems: two parallel rows on top with give underneath, which is the bought-T-shirt look.
Last reviewed 2026-08-11