What a Slip Stitch Does and When to Use It
A slip stitch is a seaming method that joins two pieces of knitted fabric with thread that runs invisibly between the edges. Unlike binding off and casting on new stitches, a slip stitch uses the existing loops along the edges of your pieces, so the seam itself becomes nearly invisible from the outside. You use it to close the sides of sweaters, join the edges of blankets, attach sleeves to bodies, or seal the opening on a stuffed toy after you've filled it.
The slip stitch works best on pieces with a clean edge—typically the selvage (the outermost column of stitches on each side of your work). It's faster and neater than grafting for most seaming jobs, and it creates a professional finish that looks like the fabric was knit as one piece rather than sewn together afterward.
Key Takeaways
- Thread a tapestry needle with yarn that matches your knit, then position the two pieces side by side with the right sides facing you.
- Insert the needle under one loop on the left piece, then under the corresponding loop on the right piece, moving upward in a straight line.
- Pull the yarn snug every few stitches so the seam sits flush against the fabric and doesn't pucker or gap.
- A slip stitch seam is complete when you've joined all the loops along both edges and the yarn runs invisibly between the two pieces.
Preparing Your Pieces and Thread
Before you begin, lay both knitted pieces flat on a table with the right sides (the outside, finished-looking side) facing toward you. The edges you're about to join should be parallel and touching or very close together. If you're joining a sleeve to a body, pin the pieces in place so they don't shift while you work.
Cut a length of yarn about 3 to 4 feet long—long enough to seam several inches without running out, but short enough that it won't tangle as you work. Thread a tapestry needle (a blunt needle with a large eye, designed for yarn) with this length. The yarn should match your knit as closely as possible; if your yarn is variegated or multicolored, choose a shade that blends with the dominant color.
If you're seaming pieces that have a selvage edge (a neat, single-stitch column along the side), position your needle so you're working into those selvage stitches. If your edges are uneven or curled, you may need to trim or block them first so the seam sits flat.
The Basic Slip Stitch Motion
Start at the bottom of your seam. Bring the needle up through the first loop on the left piece, coming from behind the fabric so the yarn emerges on the right side. This anchors your thread. Then insert the needle directly across into the first loop on the right piece, again coming from behind.
Now move upward: bring the needle back to the left piece and insert it into the next loop up, coming from behind the fabric. Then cross to the right piece and insert the needle into the next loop up there. Continue this pattern—left, right, left, right—moving steadily upward along the seam.
The key is to keep the needle moving in a straight vertical line and to enter each loop from the same direction (always from behind the fabric, so the working yarn stays hidden). If you enter loops from different angles, the seam will look uneven or twisted.
Keeping the Seam Tight and Invisible
Every 3 to 4 stitches, gently pull the working yarn snug. This draws the two pieces together and makes the seam disappear into the fabric. Don't yank—pull just firmly enough that the edges touch and the yarn sinks between them. If you pull too hard, the seam will pucker and the fabric will bunch. If you don't pull at all, gaps will form and the seam will look loose and sloppy.
As you work, the yarn should be nearly invisible from the outside. If you see a thick line of yarn running up the seam, you're either pulling too loosely or entering the loops at the wrong angle. Pause, look at what you've done so far, and adjust your tension or your needle angle before you continue.
If you're seaming a long edge and your yarn runs short, weave the end into the seam itself (run it back and forth through the stitches you've already joined) and anchor it with a small knot. Then thread a new length and continue from where you left off.
Seaming Around Corners and Curves
When you reach a corner—such as where a sleeve meets the body—slow down and count your stitches carefully. The corner should be smooth, not bunched or gapped. If you're joining a curved edge (like the cap of a sleeve) to a straight edge (like the armhole), you may need to skip a stitch on the curved side occasionally so the pieces fit together without puckering. This is called easing, and it's a judgment call based on how the fabric sits as you work.
At the very end of your seam, bring the needle through the last loop on one side, then the last loop on the other side, and pull snug. Weave the remaining yarn tail into the seam itself by running the needle back and forth through the stitches you've already joined, then trim the excess.
Common Mistakes and How to Avoid Them
The most common error is entering the loops from the front of the fabric instead of the back. This makes the yarn visible and creates a thick, obvious seam. Always come up from behind the fabric so the working yarn stays hidden between the two pieces.
Another frequent mistake is pulling the yarn too tight, which causes the seam to pucker and the fabric to bunch up on either side. Pull just firmly enough to close the gap between the pieces. If you've already pulled too tight, you can loosen it slightly by gently tugging the fabric away from the seam.
Skipping stitches or entering the wrong loop will create gaps in the seam or make it look crooked. Work slowly and deliberately, especially if you're new to the technique. It's better to seam slowly and correctly than to rush and have to pick out your work and start over.
Finishing and Blocking Your Seams
Once you've completed the seam, weave in any remaining yarn tails and give the finished piece a gentle wash if the yarn fiber allows it. Blocking—pinning the piece to shape and letting it dry—helps seams settle and look more professional. Pin the seamed garment to the dimensions you want, spray it lightly with water or steam it gently, and let it dry completely.
After blocking, the slip stitch seam should be nearly invisible from the outside and should feel smooth and flat to the touch. If you see puckering or gaps, you can sometimes improve the appearance by gently stretching the fabric perpendicular to the seam while it's still damp, then letting it dry in that position.
Frequently Asked Questions
What's the difference between a slip stitch and grafting?
Grafting (also called Kitchener stitch) joins two live stitches that are still on the needle, creating a seam with no visible row of stitches. A slip stitch joins the edges of finished pieces by sewing into the existing loops. Grafting is invisible but slower; slip stitching is faster and works on any finished edge.
Can I use a slip stitch on ribbed edges?
Yes, but it's trickier because ribbed edges have a bumpy texture. Work into the bumps (the knit stitches) rather than the valleys (the purl stitches) so the seam sits flush. You may need to ease more carefully to keep the ribbing from bunching.
What if my yarn is too thick for the tapestry needle?
Use a needle with a larger eye, or split the yarn into thinner strands before threading. Some knitters use a blunt embroidery needle or even a size-appropriate crochet hook to help guide thick yarn through the stitches.
How do I seam pieces that have different stitch counts on each edge?
Work into every stitch on the side with fewer stitches, and skip occasionally on the side with more stitches. This is easing, and it prevents bunching. Mark the midpoint of each edge with a pin before you start so you can distribute the skipped stitches evenly.
Can I use the slip stitch to join pieces that are still on the needles?
No—slip stitching requires finished edges with loops you can enter from behind. If you want to join live stitches, use grafting (Kitchener stitch) instead. You can bind off one piece and then slip stitch it to another, but you cannot slip stitch two pieces that are still being actively knit.