A stretch stitch is a special type of stitch designed for sewing flexible and elastic materials, such as knits, sweatshirt fabric, or fabrics with elastane content. A regular straight stitch is not flexible, and if you were to sew such a fabric with it, the threads would snap when the material is stretched. A stretch stitch, on the other hand, is designed to stretch along with the fabric, thereby preventing damage to the seam. On domestic sewing machines, it can take the form of, for example, a triple straight stitch, which is sewn twice forward and once backward, or a delicate zigzag stitch. This ensures both its strength and flexibility. Overlock machines, which specialize in sewing stretchy fabrics, naturally create stretch stitches thanks to their construction, which interlaces the stitch from several threads.