How the stitch is formed
One, two, or three needles create visible parallel lines while a lower looper interlaces thread across the reverse. The structure stretches without using a bobbin.
Where it is used
T-shirt hems, activewear, neckbands, elastic application, binding, and decorative reverse coverstitching are common uses. The stitch can be sewn away from a raw edge.
Coverstitch versus overlock
A coverstitch machine normally does not trim the edge while hemming. An overlocker or serger wraps and usually trims a raw edge; combination machines can provide both systems after reconfiguration.