What is a lockstitch

As its name suggests, a lockstitch is a sewing technique that locks the stitch in place.  The top thread weaves into the bottom thread and the notch on the bottom turns to grab the top thread.  This turning motion creates a loop through which the bottom thread will be dragged up and on to the bottom side of the fabric, creating a lockstitch.

Lockstitch vs. Chain Stich

Unlike a lockstitch, a chain stitch does not lock the thread in place. Instead, the two threads in a chain stitch loop around each other, creating a twisted rope affect that is commonly found on the hem of denim jeans.