Mattress stitch: the invisible seam
Mattress stitch joins two knitted pieces edge to edge with a seam that does not show. How to find the bars and sew it from the right side, step by step.
By Julia WallinCo-founder and editorMattress stitch joins two knitted pieces edge to edge. You work from the right side and sew under the bars between the edge stitch and the next stitch, alternating between the two pieces. When you pull the yarn, the seam closes and does not show on the right side. It is used for the side seams and sleeve seams of a sweater and for joining blanket strips.
Before you start
Block both pieces first if you can. Flat edges are easier to sew.
Lay the pieces side by side with the right side facing you. Match the edges row for row.
Thread a blunt tapestry needle with matching yarn.
Find the bars
Gently pull the edge stitch to the side. Between it and the next stitch you see short horizontal strands, one for each row. These are the bars you sew under. Sewing further in works, but the seam gets bulkier. Stockinette edges roll, so check that you are not inside the roll.
Sew under one bar at a time with worsted and heavier yarn, and two at a time with DK and finer yarn. Use the same number on both pieces all the way up, or the rows will not line up.
How to sew the seam
Close the bottom corner with a figure of eight. Bring the needle from back to front between the first and second stitch of one piece, just above the cast-on edge. Do the same on the other piece, then go through the first place again.
On the first piece, insert the needle under the next bar, or the next two bars, directly above where the yarn last came out. Pull the yarn through.
Do the same at the same height on the other piece.
Keep alternating. Always go in where the yarn last came out on that side.
Every few centimetres, pull the yarn gently until the bars close up and the seam disappears.
At the top, close the corner through the bound-off stitches. Weave in both ends.
Do not pull too tight. A tight seam puckers and can break when the garment is worn.
When to use it
Use it for seams along the side edges of the pieces. It works best on stockinette. The seam leaves a ridge on the wrong side and is a little less stretchy than the knitting. It uses one stitch from each edge, and patterns allow for this. To join two sets of live stitches, use Kitchener stitch.
Frequently asked questions
What is mattress stitch?
A way to sew two knitted pieces together edge to edge so the seam does not show on the right side. You sew under the bars between the first and second stitch on each edge, then pull the yarn to close the seam.
Do you mattress stitch from the right side or wrong side?
From the right side. You see the seam as you sew, so it is easy to keep the rows level.
Why is my mattress stitch seam puckering?
You have pulled the yarn too tight. Ease the seam out with your fingers until it lies flat and stretches a little.
Can I use mattress stitch on garter stitch?
Yes, but it works best on stockinette edges. On garter stitch you catch the edge in a slightly different way. The method is otherwise the same.
How much yarn do I need for seaming?
About 1.5 times the length of the seam, plus enough at each end to weave in.
Should I block before seaming with mattress stitch?
Yes, if you can. Blocked pieces lie flat, so the edges are easier to sew and the rows are easier to match.
Co-founder and editor at knyt. Knits every guide before it is published.
