The three ways to end a thread securely
A sewing thread ends when you tie it off, and the method you choose depends on whether you want the knot hidden inside the fabric or visible on the surface. The three main techniques are a knot buried between fabric layers, a backstitch lock that uses thread tension instead of a knot, and a surface knot tied on top of the fabric. Each one takes 10 to 20 seconds and works for hand sewing or machine sewing.
The buried knot is the most common choice for visible seams because the knot stays hidden. The backstitch lock is fastest on a sewing machine and requires no knot at all. The surface knot works best for temporary seams or when you want the knot to be part of the design.
Key Takeaways
- A buried knot hides inside the fabric layers and works by pulling the needle through the fold of fabric, then tying a small knot at the thread end.
- Backstitching three to four stitches in place on a sewing machine locks the thread without a knot and is the fastest method for machine sewing.
- A surface knot sits on top of the fabric and is tied by looping the thread around your needle or finger, then pulling tight.
- Thread thickness, fabric weight, and seam location all affect which method will hold best — lightweight thread on delicate fabric needs a buried knot, while heavy thread on sturdy fabric can use any method.
How to tie a buried knot for hand sewing
A buried knot is hidden between two layers of fabric, so it will not show on the finished seam. This is the standard finish for visible seams on garments, bags, and quilts. The knot sits at the point where your thread exits the fabric, so it gets trapped when you fold or press the seam.
After your last stitch, bring the needle up through the fabric but do not pull it all the way through — leave a small loop of thread on the surface. Insert the needle back down into the fabric right next to where it came up, then slide the needle forward inside the fabric layer for about one-quarter inch. Bring the needle back up through the fabric and pull the thread tight. The loop you left will form a small knot at the exit point, and that knot will be hidden between the fabric layers when you fold the seam closed.
If the knot is too large or too loose, the thread will slip out over time. To test it, tug the thread gently — it should not move. If it slides, repeat the process: make another small loop, insert the needle next to the loop, slide forward inside the fabric, and pull tight.
How to use backstitch locking on a sewing machine
A backstitch lock uses the sewing machine's reverse function to lock thread in place without tying a knot. This method works only on a sewing machine, not by hand, and is the fastest way to finish a seam. Most machines have a backstitch button or lever on the front or side.
When you reach the end of your seam, press the backstitch button and sew backward for three to four stitches, then release the button and continue forward for three to four stitches. This creates a tight cluster of overlapping stitches that locks the thread. The overlapping stitches are stronger than a knot because they distribute tension across multiple thread crossings instead of one point.
Backstitch locking works best on medium to heavy fabric and thread. On very delicate fabric or thin thread, the overlapping stitches can pucker the fabric. If puckering happens, use a buried knot instead, or reduce the machine tension slightly before backstitching.
How to tie a surface knot for temporary seams
A surface knot sits on top of the fabric and is visible from the outside. Use this method for basting stitches, temporary seams, or when the knot is part of the design. A surface knot is faster to tie than a buried knot and works well on thick or textured fabric where a buried knot might slip.
After your last stitch, bring the needle up through the fabric and pull the thread all the way through. Wrap the thread around the needle shaft two or three times, then push the needle back down through the fabric close to where it came up. Pull the thread tight — the wraps around the needle will form a knot on the surface of the fabric. Trim the thread tail to one-quarter inch.
Surface knots can loosen if the thread is pulled sideways, so avoid this method on seams that will bear stress. For a stronger surface knot, wrap the thread around the needle four times instead of two or three, but do not wrap more than four times or the knot will be too bulky to pull through the fabric.
Common mistakes that cause threads to come loose
The most common mistake is pulling the thread too hard when you tie the knot. If you pull with force, the thread stretches and then relaxes later, leaving slack in the knot. Pull the thread firmly but not hard — you should feel resistance, not a snap. The second mistake is leaving the knot too far from the fabric. If the knot is one-half inch away from the seam, it will not catch the fabric and will slip out. The knot must touch the fabric or be buried inside it.
A third mistake is using thread that is too thin for the fabric weight. Lightweight thread on heavy fabric will break under stress before the knot fails, but the break will happen at the weakest point — often at the knot itself. Match thread weight to fabric: use lightweight thread on cotton voile or silk, medium thread on cotton or linen, and heavy thread on denim or canvas.
Finally, do not trim the thread too short. Leave at least one-quarter inch of thread tail after you tie the knot. If you trim flush to the knot, the knot can unravel as the fabric moves and stretches.
Which method to use for different fabrics and seams
Lightweight fabrics like cotton voile, silk, or chiffon need a buried knot because the fabric is too delicate to hold a surface knot. The buried knot distributes the knot's tension across the fabric layers instead of concentrating it at one point. Backstitch locking can work on lightweight fabric if you reduce the machine tension first, but a buried knot is safer.
Medium-weight fabrics like cotton, linen, and wool work with any method. Use a buried knot for visible seams, backstitch locking for machine sewing, or a surface knot for basting. Heavy fabrics like denim, canvas, and upholstery fabric hold all three methods equally well, so choose based on speed — backstitch locking is fastest on a machine, and a surface knot is fastest by hand.
Seams that will bear stress, such as underarm seams on a garment or stress points on a bag, should use either a buried knot or backstitch locking. Surface knots can loosen under repeated pulling or stretching. Decorative seams or seams on the inside of a garment can use any method.
How to fix a thread that came loose
If a seam starts to unravel, you can repair it without taking apart the entire seam. Thread a needle with a length of thread that matches the original thread color. Starting at the point where the seam is coming loose, insert the needle into the fabric and make small stitches along the seam line for about one inch past the loose area. Then tie off the thread using a buried knot or backstitch lock.
If the seam has unraveled more than one inch, it is faster to remove the entire seam and re-sew it. Use a seam ripper to cut and remove the old thread, then sew the seam again using the same method you used the first time. If the original method failed, choose a different one — for example, if a surface knot came loose, use a buried knot instead.
Frequently Asked Questions
Can I use the same knot method for hand sewing and machine sewing?
No. Backstitch locking only works on a sewing machine because it requires the reverse function. For hand sewing, use a buried knot or surface knot. For machine sewing, you can use backstitch locking, or you can hand-tie a buried knot after removing the fabric from the machine.
What if my thread keeps slipping out of the knot?
The knot is either too loose or too far from the fabric. Pull the thread tighter when you tie the knot, and make sure the knot touches the fabric or is buried inside it. If the thread is very slippery (like silk or polyester), wrap it around the needle one extra time before pulling tight.
How short can I trim the thread after tying a knot?
Leave at least one-quarter inch of thread tail. If you trim closer than that, the knot can unravel as the fabric moves. For delicate fabrics, leave one-half inch to be safe.
Do I need to tie a knot if I'm using a sewing machine?
No. Backstitch locking locks the thread without a knot and is the standard method for machine sewing. You only need to tie a knot by hand if you prefer it or if your machine does not have a backstitch function.
What's the difference between a buried knot and a backstitch lock in terms of strength?
Both are equally strong when done correctly. A buried knot concentrates tension at one point, while a backstitch lock spreads tension across multiple stitches. On delicate fabric, a buried knot is safer because it does not pucker. On heavy fabric, both methods hold equally well.