How to mattress stitch your knits
Published on 28 March 2019 2 min read
So you’ve decided to knit a snuggly jumper, and you’ve done an amazing job so far. Except your jumper is still in several pieces, and now you need to sew it up! Don’t worry – we’ve all been there, and once you’ve mastered how to mattress stitch, you’ll be good to go.
Follow our super easy step-by-step guide to mattress stitch knitting and you can finish up projects with invisible stitch lines and a perfect professional finish!
What is a mattress stitch?
A mattress stitch is a vertical invisible seam that joins two knit pieces together side by side. The seam itself is flexible, neat and firm, making it perfect for finishing up several projects – from jumpers and cushions, to that vibrant patchwork blanket you’ve always wanted to finish.
When should I use a mattress stitch?
A mattress stitch only works when the two pieces have an identical number of stitched rows. It’s perfect for patterns that use the stockinette stitch or ribbing. You’ll want to use it whenever you’re looking for a flat join. Because the stitch is externally invisible, it can even come in handy to make any necessary size adjustments.
How to mattress stitch step-by-step
Lay down the knitting.Place the two pieces to be joined side-by-side, with the right side facing you.
Cut your yarn.As we want this stitch to be invisible, use the same yarn you’ve knitted with (though we’ve used contrasting yarn to show you how to do it). Measure out a piece about three times the length of the seam you want to join, and thread it through a blunt darning needle.
Thread your yarn through the first stitch.Beginning with the left side of the knitting, take your darning needle and insert it into the bottom right hand corner of the first stitch.
Insert your needleupwards from back to front.
Repeat on the right side.Find the first stitch on the bottom left, and insert your needle from back to front.
Thread back through your first hole.Go back into the same hole as you originally inserted your needle through from back to front, and pull the yarn through. Great work: you’re ready to start your mattress stitch!
Thread beneath the two bars.If you pull your knitting slightly apart you will see two horizontal bars. Take your darning needle and thread it beneath the two bars, pulling it through from front to back.
Continue in the same pattern.Match the rows from each side as you zig zag from edge to edge for about 2 inches.
Pull the thread up.Hold the base of the seam until the seam is joined and the stitches become invisible. Try not to pull it too tightly as you don’t want to distort your work.
Continue to the top.Secure the ends by sewing them in. You should be left with a perfectly flush finish, and invisible seam line.
How to Join Knitted Pieces with the Mattress Stitch
Mattress stitch makes a practically invisible and nicely flexible seam for joining pieces side to side. You can’t use mattress stitch successfully, however, on pieces that don’t have the same number of rows or a difference of only 1 or 2 rows.
1 Lay out your pieces next to each other, right sides facing up, bottom edges toward you.
You seam from the bottom edge up. If you’ve left a tail of yarn at the cast-on edge, you can use it to get started.
2 Locate the running thread between the first and second stitches on the bottom row of one piece.
Gently pull apart the first 2 edge stitches to see the series of little horizontal — running — threads connecting them.
3 Thread the tail of yarn or a fresh piece on a tapestry needle.
Make sure your tapestry needle is blunt to avoid piercing the yarn.
4 Join the bottom edges of the pieces, using a figure eight.
Work through the two threads on the cast-on row.
5 Bring your needle under the thread; then pick up the running thread between the first and second stitches on the opposing piece.
This step begins your mattress stitch pattern.
6 Work back and forth from running thread to running thread to running thread, keeping the tension easy but firm.
Check the tension by pulling laterally on the seam from time to time. The amount of give should be the same as between 2 stitches.
The Mattress Stitch is a finishing technique for vertical seaming. It creates an invisible join between pieces worked in stockinette stitch or ribbing, perfect for so many things, such as sewing the front and back of a sweater together. For demonstration purposes, we have used a different yarn in a contrasting color, but typically you would use the same yarn as your knit pieces.
First, align the two pieces you wish to seam. Bring your threaded tapestry needle from the back of your work to the front at the location where you wish your seam to start. (I began with the knit piece to the right and brought my needle to the front just above my cast on edge.)
For Mattress Stitch you sew two knit pieces together by grabbing a strand of yarn from each edge, alternating back and forth, working vertically along the edges. The strand of yarn you grab is a horizontal bar that runs between the knit stitches (or “V”s). If you gently tug on the right and left edge of your knit piece, you can see these horizontal bars (or “ladder”) between the Vs. Picking up a bar from each side draws the edges together, making it appear as though it is one knit piece.
Next, draw the needle under the bar between the two most outer Vs of the second knit piece, right across your entry of the first edge. Beware of the outermost column of knit stitches; it tends to curl to the back. The farther in from the edge that you work, the bulkier the seam will be.
Take the tapestry needle back to the first piece and pick up the bar just above your initial entry point.
Now, take the needle back to the second piece and pick up the bar above the last one your picked up on this side.
NOTE: Depending on the gauge or density of the fabrics, sometimes it is just as effective to pick up every other bar, rather than ever bar. It is a personal choice.
Continue working vertically along the two edges, drawing the tapestry needle under each bar of each piece.
Above you can see the many red stitches connecting the two columns of Vs. The goal is to bring those Vs together.
Just as with knitting, the more even you can keep your tension, the better. An even tension will prevent pulling and puckering along the seam.
To close the seam, gently pull the length of yarn from either the top or the bottom. If you are working a long seam, it is best to sew a few inches, then pull to close, again sew a few inches and pull, continuing in this fashion to the end of the seam, being careful to maintain a consistent tension throughout.
If you turn your work over so the wrong side is facing, you’ll see the seam.
Mattress Stitch On Ribbing
Learn how-to make a mattress stitch on ribbing with The Sheep Shop, Cambridge
This tutorial shows two ways to sew together single ribbing (K1, P1) using mattress stitch: using the running threads between stitches or sewing two halves of two knit columns together. Mattress stitch is an invisible (from the right side) join between the sides of two pieces of knitting. Exactly the same principles can be used to sew double ribbing, you just choose where you want to put the seam line for a seamless-looking join.
If your pattern has added no selvedge stitches, your ribbing will usually either start and end with a knit stitch or one edge will be a knit, the other a purl. Here we will use the running threads to join a knit edge to a purl edge and the knit columns to join a knit edge to a knit edge. You can use either method as you see fit. I find the second method a little easier but the seam is bigger (unless you start and end with a purl). Having two knit stitches on each edge and using the running threads between them is also good.
The yarn used here is Hjertgarn Woolcott, a machine-washable 55% lambswool, 45% cotton DK. It was knitted very loosely in order to make it easier to take pictures.
Tips for mattress stitch
To sew up, use the same yarn as you used for the project unless it is very thick yarn.
Unless it’s just a little seam, do not use a dangling tail in case you need to reknit a bit, you’ll have to unpick the whole seam first. Instead, cut a piece of yarn about twice as long as the length of the seam.
For long pieces, use safety pins or butterfly hairclips to align the garment corners and some key points in the middle.
When your needle gets to one of these markers on one side you should reach it at the other side on the next stitch – if
not, you’ll be ending up with a piece of knitting looking like a shirt with its buttons done up into the wrong button holes. If you do end up a bit skeewiff, do a couple of bars on one side and just one on the other a few times, but spread this out, don’t bunch it all into the next few stitches.
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You Will Need
Running thread join
Running threads are the pieces of yarn which connect a stitch to its neighbour. You can think of a stitch as a horseshoe with the open bit at the bottom. For a knit stitch, the top of the horseshoe (the stitch head) is slanted to the back and you can clearly see its legs facing you. For a purl stitch you can see the stitch head but the legs are on the other side of the work. For the running thread join you simply sew under a running thread on one piece of knitting then sew under a running thread on the other piece, working your way steadily upwards.
Please insert pictures rt1 – rt8
First you need to secure your yarn with a figure of eight join. With right sides up, bring the needle up from back to front by the bottom corner stitch on the left side piece of knitting, then reach around the back and come up through the same hole. The yarn is now secured to one piece of knitting. Leave a long enough tail that you can weave it in later.
Now bring the needle up from back to front by the bottom corner stitch on the right piece of knitting. Now up again through the same hole on the left piece. See the figure of eight?
With RS up, pass the needle under the first two running threads on the right hand piece (you put the needle in where it came out before). Your needle stays at the front of the work, you never need to pass it all the way through the knitting.
Then pass the needle under the first two running threads on the left hand piece. Put the needle back where it came out on the right side and pass under another two bars. Put the needle back where it came out on the left side and pass under another two bars. Keep repeating this.
After a couple of inches, pull the thread taut and the sides will zip up together seamlessly (pull it back if it gets too tight).
When you’ve sewn under the last running bars on the right side and the left side, and pulled taut your yarn, you’ll probably find it looks a bit scruffy. Now you do put your needle all the way through your knitting. If you’e done the last running bar on the left, put your needle back where it came out on the right and sew all the way through.
You now have a knit column on one side abutting a purl column on the other. If the colours were the same, you’d never know there was a join. The two edge stitches have curled inward to form a small seam on the WS. Now weave in your ends on the WS.
Joining knit columns
Here a knit stitch edge is being joined to a knit stitch edge. You could use the running thread join above, this will give a small seam on the inside as there will be one stitch from each side. If you join knit columns instead, you can either work up the very edge stitches to give a very small seam on the inside but it can be tricky to do and look sloppy. Easier is to work up the knit columns one further in, though you will get a big seam on the inside.
Start by securing your yarn to the left hand piece and making a figure of eight join. You don’t want to work one stitch in – this time your needle comes out in the centre of the bottommost stitches of the knit columns you will be sewing together.
With RS up, pass the needle under the first two stitch heads on the right hand piece. Your needle stays at the front of the work, again you never needs to pass it all the way through the knitting.
Put your needle back where it came from on the left piece and pick up two stitch heads on that side. Then back to where your yarn comes out on the right. exactly as before just you are working within the column of knit stitches instead of the running threads which join them.
When you get to the top, sew through all the way same as before and weave in your end on the WS.
You now have a neat seam on the RS and a bigger seam on the WS.
How to Join Knitted Pieces by Sewing with Backstitch
When you join knitted pieces by using backstitch, you sew them together in the conventional manner. Backstitch involves placing the right sides of your pieces together and moving your tapestry needle in and out along the seam line.
1 Pin the pieces right sides together.
If you haven’t counted rows and one piece is slightly longer or wider than the other, you have to ease in the extra fabric so the pieces begin and end in the same place.
2 With a tapestry needle and yarn, bring the needle from the bottom up through both layers 1 stitch in from the edge.
Pass the needle between the strands of yarn, not through strands.
3 Go around the edge, come out in the same spot to secure the end of the yarn, and bring the bottom edges of the pieces together.
This step begins to form the binding stitch
4 Go around again and come out 1 stitch farther up from the initial stitch.
You can begin to see the way that the backstitch joins the knit pieces.
5 Insert the needle back through the initial stitch and bring the tip out through both layers again
Bring the tip out a few stitches from where it last came out.
6 Continue in this manner — going forward, coming back — and keep an even tension.
Bring your needle in and out in the spaces between stitches and avoid splitting the working yarn. Also, give your knitting a gentle stretch while you work to keep it flexible.