A lockstitch is the most common mechanical stitch made by a sewing machine.  It differs from a chain stitch in that there is no chain on the underside of the stitched fabric.  Chain stitching machines are mostly handheld or children’s sewing machines.  Most of the industry use only lockstitch machines.

When sewing with a lockstitch the tension must be even on both the top and bottom thread.  It is suitable for stretch fabrics, and any other available fabrics on the market today.

The chain stitch is very good for making bathing suits, and for very stretchy fabric because the chain on the underside has more give to it.