The three main ways to join knitted pieces
You join two finished knitted pieces by grafting, seaming, or binding them together. Grafting (also called Kitchener stitch) creates an invisible seam by threading yarn through live stitches on both pieces. Seaming uses a needle and yarn to stitch the edges together from the outside or inside. Binding uses a cast-on edge or ribbing to connect pieces, and is most common when joining sleeves to a body or adding a collar.
The method you choose depends on where the seam will be, how visible it should be, and whether your pieces have live stitches (stitches still on the needle) or finished edges. Most garments use a combination—grafting for shoulders, seaming for side seams, and binding for necklines.
Key Takeaways
- Grafting with Kitchener stitch joins live stitches invisibly and works best for shoulders and horizontal seams where both pieces have stitches still on the needle.
- Mattress stitch seaming creates a strong, nearly invisible seam on vertical edges like side seams and is worked from the inside of the fabric.
- Binding off together joins two pieces by working new stitches across both at once, and is the standard method for attaching sleeves and collars.
- You need a tapestry needle (blunt, with a large eye), yarn that matches your project, and either live stitches or finished edges depending on your method.
- Practice on a small swatch before joining your finished pieces, because seams are harder to undo than cast-on rows.
Grafting with Kitchener stitch for invisible horizontal seams
Kitchener stitch joins two pieces of knitting so seamlessly that the join looks like a row of knitting itself. It works only when both pieces have live stitches—stitches that are still on the needle and have not been bound off. This is the standard method for joining shoulder seams and for closing the top of a hat.
Thread a tapestry needle with a length of yarn about 18 inches long (or longer if your seam is wide). Hold the two pieces with the needles parallel, tips pointing to the right, with the working yarn attached to the right piece. Insert the tapestry needle through the first stitch on the front needle from front to back, then through the first stitch on the back needle from back to front. Now work in a pattern: bring the needle through the front needle stitch again from back to front and slip it off, then through the next front stitch from front to back. Move to the back needle, bring the needle through from front to back and slip it off, then through the next back stitch from back to front. Repeat this pattern across the entire seam.
The rhythm is: front stitch off, back stitch off, front stitch on, back stitch on. Keep the tension loose enough that the yarn slides easily but tight enough that the finished seam does not gap. After you finish, gently pull the yarn to tighten the seam, then weave the tail into the fabric on the inside.
Mattress stitch for nearly invisible vertical seams
Mattress stitch creates a seam that runs up the side of your knitting and is nearly invisible from the outside. It is the best choice for joining the sides of a sweater body or the seams of a sleeve. Unlike Kitchener stitch, mattress stitch works on finished edges—you do not need live stitches.
Lay the two pieces flat with the right sides facing up and the edges you want to join side by side. Thread a tapestry needle with a length of yarn. Starting at the bottom, insert the needle under the horizontal bar of yarn that runs between the first and second stitch on one piece, then under the corresponding bar on the other piece. Move up one row and repeat, going back and forth between the two pieces. Every few rows, gently pull the yarn to close the gap between the pieces. The seam will disappear into the fabric as you pull.
Work from the inside of the garment if possible, so you can see the seam close as you go. If you are joining stockinette stitch (the smooth, V-patterned fabric), the seam will be nearly invisible. Mattress stitch works less well on textured stitches like garter stitch, where a backstitch seam is often clearer.
Binding off together to attach sleeves and collars
Binding off together joins two pieces by working new stitches across both at the same time. This method is used to attach sleeves to an armhole, a collar to a neckline, or a ribbed band to an edge. One piece will have live stitches on a needle; the other will have a finished edge (usually a cast-on or bind-off edge).
Pick up new stitches along the finished edge using a knitting needle and yarn. You will pick up one stitch for every row on the finished edge, or follow the pattern instructions for how many stitches to pick up. Once you have the same number of stitches on both needles, hold the needles parallel and bind off both pieces together using a three-needle bind-off. Insert a third needle through the first stitch on the front needle and the first stitch on the back needle, knit them together, then repeat with the next stitches. Pass the first stitch over the second to bind off, just as you would for a normal bind-off.
The three-needle bind-off creates a ridge on the inside of the garment. If you want a flatter join, pick up stitches and work a few rows of ribbing or garter stitch before binding off, then seam that band to the garment using mattress stitch.
Backstitch seaming for durability on textured fabrics
Backstitch seaming is a straightforward, strong seam that works on any knitted fabric, especially textured stitches where mattress stitch is hard to see. It creates a visible ridge on the inside of the garment and is often used on the seams of hats, bags, or garments where the inside will not be seen.
Lay the two pieces with right sides together (the pretty sides facing each other). Thread a tapestry needle and insert it through both layers about half a stitch in from the edge. Bring the needle back out one stitch forward, then insert it back into the hole you just came out of. Move forward one stitch and repeat. The seam will run along the edge of the fabric and will be visible from the inside.
Backstitch is faster than mattress stitch and does not require you to see inside the fabric, so it is useful when you are seaming a closed tube or a tight space. The trade-off is that the seam is thicker and more visible, so it is best used where appearance matters less than strength.
Preparing your pieces and choosing yarn for seaming
Before you seam, lay out both pieces and check that the edges are even and the dimensions match. If one piece is slightly larger, you can ease the extra fabric in as you seam by taking slightly smaller stitches on the larger piece. Block your pieces if the pattern calls for it—blocking evens out the stitches and makes seaming much easier.
Use yarn that matches your project yarn as closely as possible. If your project yarn is thick or textured, you can use a thinner yarn in the same color for seaming, because the seam yarn will be hidden inside the fabric. If you are using a dark yarn and a light yarn, test the seam on a swatch first to make sure the seam yarn does not show through. Always use a tapestry needle (blunt, with a large eye) rather than a sharp needle, because a sharp needle will split the yarn fibers and create a weak seam.
Common mistakes and how to avoid them
The most common mistake is pulling the seam yarn too tight, which puckers the fabric and makes the seam stiff. Pull just hard enough to close the gap between the pieces, then stop. If you have already pulled too tight, you can sometimes loosen it by gently stretching the seam with your fingers.
Another mistake is seaming too close to the edge of the fabric. If you seam right at the edge, the seam will be weak and the edge stitches will unravel. Leave at least half a stitch between the seam and the edge. For mattress stitch, work under the horizontal bars one stitch in from the edge, not at the very edge itself.
Mismatched stitch counts will cause bunching or gaps. If you are binding off together, count the stitches on both needles before you start. If you are picking up stitches, pick up one stitch for every row on the finished edge, or follow your pattern. If the numbers do not match, you can decrease or increase a few stitches before you bind off.
Frequently Asked Questions
Can I use regular sewing thread instead of yarn to seam?
No. Sewing thread is too thin and will break under the stress of wearing a knitted garment. Always use yarn that matches your project weight and fiber content. If your project yarn is very thick, you can use a thinner yarn in the same color, but it should still be a knitting yarn, not sewing thread.
What do I do if I seamed two pieces together and they do not line up?
If the pieces are only slightly off, you can sometimes adjust the seam by easing in the extra fabric as described above. If they are badly misaligned, you will need to undo the seam and try again. Use a seam ripper or small scissors to cut the seam yarn every few stitches, then pull out the yarn and pick up the live stitches with a needle before reseaming.
Should I seam before or after blocking?
Block first if your pattern calls for blocking. Blocking evens out the stitches and makes the pieces the correct size, so seaming after blocking will be easier and the finished garment will fit better. If you seam before blocking, the seams may pucker or stretch unevenly when you block.
How do I hide the seam yarn tail after I finish seaming?
Thread the tail onto a tapestry needle and weave it through the stitches on the inside of the garment, going back and forth for about 2 inches. Then trim the tail close to the fabric. The woven-in yarn will stay in place and will not unravel.
Can I use Kitchener stitch on pieces that have been bound off?
No. Kitchener stitch requires live stitches on both pieces. If your pieces are already bound off, you will need to pick up stitches along the bind-off edge using a needle and yarn, then use Kitchener stitch. Alternatively, use mattress stitch or backstitch seaming on the finished edges.