Chain stitching is a type of stitch that can be made by a sewing or embroidery machine. The name "chain stitch" comes from the way it looks, like a looped chain. In sewing, a chain stitch looks like a looped chain on the bottom and a single stitch line on the top.
A chain stitch is a form of stitching in which one continuous thread is looped back on itself, with no bobbin thread in between. Chain stitches are more flexible than lock stitches, which is why they're used in areas like jeans' waistbands and leg seams. Chain stitching is a classic hem stitch that provides a vibrant rope effect. It is constructed with a single continuous thread that loops back on itself. The characteristic rippling on the hem is caused by using a chain stitch, which pulls slightly on the denim. All of these machines do chain stitching. It looks like a regular stitch on the right side.
The traditional way to hem jeans is with a stitch called "chain stitching," which looks like a rope. It uses one thread that keeps going and goes back on itself. When you use a chain stitch, the denim is pulled a little bit, which is what gives the hem its characteristic ripples.
Most jeans without chain stitching are made by new denim brands or designers who haven't worked with denim much before. But being a beginner is not the rule. Even the most popular and well-known brands sometimes use factories that are used to making cheap or discount denim, and chain stitching is usually ignored if it's not part of the design.