When you sew, there is both a starting and an ending point to a seam. To prevent those points from unraveling and stretching out of shape, you need to secure them with a back stitch or lock stitch.
Backstitching is done by sewing backward and forward at the beginning and end of a seam, on top of the seam stitches, to prevent the stitching from coming undone. If you are sewing with a very fine fabric you might not like how backstitching leaves a relatively large amount of thread that can show through the fine fabric, or change the way fabric drapes or hangs. In those cases, use a lock stitch instead.
In other cases, it is best to sew off the fabric, leaving a long tail of thread, and then knot the thread by hand. Sewing a dart is an example of using this technique. Backstitching or a lock stitch would leave an unsightly lump at the pointed end of a dart, but sewing off the end of the point allows for a smooth transition.
How to Sew a Back Stitch
Every model of a sewing machine is a little different but the basics are the same. An industrial sewing machine or a very old home sewing machine may not offer the option of sewing in reverse. In this case, you can leave the needle down and change the direction of the fabric to obtain the same result. The manual for your sewing machine is the best source of guidance. If you don't have the original manual, you can find replacement manuals online.
- When beginning a seam, place the entire piece of fabric under the presser foot with the fabric aligned with your seam guide and the back of the presser foot.
- Sew in reverse for a couple of stitches to the end of the fabric.
- Stop and sew forward for the length of the seam, keeping the seam guide lined up to sew a consistent seam allowance.
- Sew to the end, stop, and sew in reverse for a couple of stitches.
- Always press your seams and apply a seam finish.
How to Sew a Lock Stitch
A built-in lock stitch feature on a sewing machine sews a certain number of stitches and then stops sewing. This option is available on many newer electronic sewing machines. Quilters use this feature to secure quilting stitches without having an unsightly back stitch visible on their quilts. A lock stitch is also used on sheer fabric and fabric that tends to have a large amount of sweeping drape, since backstitching could interfere, even in a small way, with the natural drape of the fabric.
- On a sewing machine that has a built-in lock stitch feature, refer to your sewing machine manual. The lock stitch feature sews the same single stitch backward and forward without repeated stitches.
- On a sewing machine that does not have a built-in lock stitch feature, you can achieve the same result by shortening the stitch length to as short as possible and sewing two to four stitches in that one spot. More than that is apt to jam the machine and create an unsightly thread knot.
- It also is possible to stop the sewing machine stitching, leave a thread tail and then pull one tail to the back side and hand knot the thread tails tight to the fabric.