The basic finish: backstitching at both ends

The simplest way to finish a seam is to backstitch — sew backward over the last few stitches you just made. This locks the thread so it cannot pull loose when the garment is worn or washed. On most machines, you hold down the reverse button (or lever, depending on your model) while sewing backward about half an inch, then release it and continue forward with your next seam.

Do this at the start of every seam and at the end. If you skip the backstitch at the beginning, the first few stitches will come undone the moment someone pulls on that seam. At the end, the same thing happens — the thread straightforward slides out of the fabric. Backstitching takes three seconds and prevents hours of repair work later.

Some machines have an automatic backstitch button that does this for you when you press it. Check your manual to see if yours does. If it does, use it — it is faster and more consistent than doing it by hand.

Key Takeaways

  • Backstitch at the start and end of every seam by sewing backward a half inch, which prevents the thread from unraveling when the garment is worn.
  • Trim loose thread tails to about a quarter inch after backstitching, so they do not catch on fabric or get tangled in the machine.
  • For seams that will take hard wear — like underarms or crotch seams — use a second row of stitching parallel to the first, called a reinforcement stitch.
  • Knot thread by hand if you are hand-sewing, or use a needle threader and pull the thread tight before cutting.
  • Seams in stretchy fabrics like knit or swimwear need a zigzag stitch or a special stretch stitch instead of a straight stitch to prevent popping.

Trimming thread tails

After you backstitch, you will have loose thread hanging from both ends of the seam. Cut these as close to the fabric as you can — ideally a quarter inch or less. Leave them longer and they catch on other fabric, get tangled in the machine, or work their way loose over time.

Use small, sharp scissors or thread snips. Dull scissors will fray the thread and make it harder to trim cleanly. If you are working with delicate fabric like silk or linen, be careful not to nick the fabric itself when you cut.

Reinforcing seams that take hard wear

Some seams fail more often than others because of the stress they take. Underarm seams, crotch seams, and the seams where sleeves attach to a shirt all move constantly and bear weight. For these, a single row of stitching is not always enough.

To reinforce, sew a second row of stitches parallel to the first, about an eighth inch away. This does not have to be perfect — it just needs to be close. You can do this on the same side of the fabric as the first seam, or on the back side if you want it hidden. Either way, the two rows of thread lock the fabric together much more securely than one row alone.

Some sewers use a zigzag stitch for the second row instead of a straight stitch. This adds even more grip and is especially useful in knit fabrics that stretch.

Finishing seams in stretchy fabrics

Cotton and linen seams hold together with a straight stitch and a backstitch. Knit fabrics, swimwear, and anything with spandex do not. When you stretch the garment, a straight stitch breaks because the thread cannot move with the fabric.

For stretchy materials, use a zigzag stitch instead of a straight stitch. The zigzag moves with the fabric and does not snap. Many machines also have a special stretch stitch or elastic stitch — check your manual to see if yours does. These are designed specifically for knits and swimwear and work better than a regular zigzag.

Backstitch at the start and end of a zigzag seam the same way you would for a straight seam. The reverse button works the same way.

Hand-sewing a finished seam

If you are sewing by hand, finish the seam by knotting the thread. Push the needle through the last stitch, then loop the thread around the needle shaft and pull tight. Do this twice — once to find the knot, and once more to make sure it holds.

Trim the thread tail to a quarter inch. If the knot is too large or visible, you can hide it by running the needle through the seam allowance (the fabric between the seam and the edge) for an inch or so before you cut. This buries the knot inside the garment where it cannot be seen or felt.

Finishing raw edges to prevent fraying

Backstitching and knotting hold the seam together, but they do not stop the raw fabric edges from fraying. Over time and with washing, the cut edges of the fabric will shed fibers and look ragged.

To prevent this, trim the seam allowance (the fabric on either side of the stitching line) with pinking shears — scissors with a zigzag blade. The zigzag edge does not fray as quickly as a straight cut. Alternatively, use a zigzag stitch along the raw edges after you have sewn the seam. This seals the fibers and keeps them from coming loose.

For garments that will be washed often or worn hard, you can also use a serger (a special machine that cuts and seals edges in one step) or bias tape (a strip of fabric sewn over the raw edge). These methods take more time but create a much more durable finish.

Frequently Asked Questions

What happens if I forget to backstitch?

The thread will unravel from that end the first time the seam is pulled or the garment is washed. The stitches will come out one by one until several inches of seam are undone. You will have to re-sew that section. Backstitching takes three seconds and prevents this entirely.

Can I use a knot instead of backstitching on a machine?

No. Machine stitches are not designed to hold a knot. Backstitch is the correct way to lock machine stitches. If you knot the thread before putting it in the machine, the knot will jam in the needle or bobbin and break the thread.

How short can I trim the thread tails?

Trim them as short as you can without cutting the fabric itself — a quarter inch is ideal. If you leave them longer than half an inch, they tend to catch and unravel. If you cut too close, you risk nicking the fabric or having the thread pull out of the backstitch.

Do I need to finish the raw edges of every seam?

Not always. Seams inside a garment that will not be seen or touched do not need finished edges. Seams on the outside, or seams that will be washed often, should be finished with pinking shears or a zigzag stitch to prevent fraying and keep the garment looking neat.

What is the difference between a backstitch and a reinforcement stitch?

A backstitch locks the thread at the end of a seam so it does not unravel. A reinforcement stitch is a second row of stitching that runs parallel to the first seam and makes it stronger. You use both — backstitch to lock the thread, and reinforcement stitches on seams that take heavy wear.