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Master Class: Seaming Set-In Sleeves

Updated: Jul 21, 2023

Set-in sleeves give such a tailored look to a sweater! How you seam the sleeve makes a big difference in the final appearance. Follow these tips for a more polished look and better fit:

Wet block all pieces to the measurements given in the schematic. Pin each piece in place, using your fingers to uncurl the first and last stitches so you have flat working areas. Once dry, unpin, shake out, and lay out each piece with right sides facing up.

Measure yarn that is about three times the edge of the sleeve cap by draping yarn back and forth from underarm to underarm, around the cap three times, then cut and thread onto a tapestry needle.

Fold the sleeve cap in half (with underarms together) to find the center of the top of the sleeve cap and pin this to the center of the shoulder seam. (We'll start seaming here.) Using anything that holds fabric together (straight pins, safety pins, locking stitch markers, open slotted stitch markers), pin the back half of the sleeve cap in place from shoulder seam to center of the underarm, aligning the bind off edges.

Seam the back side first, using Mattress stitch. Start at the top (center of shoulder seam) insert tapestry needle from back to front through the center of the V of the center stitch if there‘s an odd number of stitches, or into the center of the V to the right of the center marker if there’s an even number. Next, insert needle in between first and second stitch of shoulder at seam, picking up the horizontal bar. Pull yarn through until half of the yarn is on each side. Set half of the yarn aside which will be used to seam the front half of the sleeve.

Seam top of sleeve cap (horizontal edge) to top few rows of armhole (vertical edge). Count the number of stitches at the top of the sleeve cap (same as your final bind off number). In this example, we have 14 stitches, 7 stitches to each side of the center mark. Since your pieces are pinned nice and flat, count the number of rows between these 14 stitches. In this example, we have 18 rows, 9 rows on each side of the shoulder seam. We need to pick up 14 stitches over 18 rows. 18-14 = 4 rows need to be skipped during our seaming. We skip rows by going under 2 horizontal bars instead of 1, so we will pick up 2 horizontal bars 4 times. To determine the spacing interval, 14 ÷ 4 = 3.5 so we need pick up 2 bars on the body every 3rd row then every 4th row. The layout across the top of the sleeve cap will look like this:

Reading from right to left, we are picking up 1 stitch/1 bar three times, then 1 stitch/2 bars on the 4th time. Pick up 1 stitch/1 bar two times, then 1 stitch/2 bars on the 3rd time.

Since we are starting in the center, and working out to the right, start by picking up 1 stitch/2 bars at the center, then 1 stitch/1 bar two times, then 1 stitch/2 bars, then 1 stitch/1 bar three times. This maintains an even pick up ratio across the whole top of the cap.

When the back is seamed, return to the center, pick up the second half of the seaming yarn, and work out to the left by picking up 1 stitch/1 bar three times, then 1 stitch/2 bars, then 1 stitch/1 bar two times, then 1 stitch/2 bars.

Make sure you're inserting the needle into the proper spots. When seaming a sleeve cap, you will seam along horizontal, vertical and diagonal edges. If you look at the knitting, you’ll see that each stitch forms a V. Read on for more detail on each! (And click here for more information on picking up stitches properly.)

Seaming Along a Horizontal Edge

The sleeve cap will have horizontal edges at the top and bottom bind off sections. Insert tapestry needle into the center of the stitch, or the center of the V, just below the bind off edge and come up through the center of the stitch next to it. One stitch has been picked up.

Seaming Along a Vertical Edge

Move to the garment’s body and now we are seaming to a vertical edge. With vertical edges, you’re going to insert the needle tip between the body's 1st stitch (selvedge stitch) and 2nd stitch. This places the first column of stitches on the body inside the seam. The second column of stitches now becomes the edge column of stitches that you see. We are picking up the horizontal running bar that connects the 1st and 2nd stitches. Look at the armhole with the top at the top, and the bottom at the bottom, and you can see that the tapestry needle is coming in between the column of stitches.

But since we are starting from the center of the cap and working from the top down, when we turn our work upside down, it looks as if the needle is coming out of the center of the stitch or V. Once you understand how this looks as you are seaming, you can move along quickly without having to stop and turn your work.

Handling Stair Steps

When you have sections that are bound off instead of decreased, take the tapestry needle from the center of the V at the upper row, down to the center of the V which will be 2 rows below. Do not insert needle into gap between the rows. It seems like a big jump but if you go into the hole you’ll just make it bigger. Once the seaming thread is pulled tight, the stair step disappears and a slant appears.

Seaming Along a Diagonal Edge

Once you reach the diagonal slant, you are picking up both the sleeve cap and the body using the vertical method. Before beginning, count the number of rows in the diagonal section of the sleeve cap, stopping at the beginning of the bind off stair steps. In this example, there are 23 rows along diagonal edge. Next, count the number of rows in the armhole, and we have 30 here. 30 – 23 = 7. We are going to skip 7 bars which means going under 2 bars 7 times. To find out the ratio, 23 ÷ 7 = 3. We will pick up 1 bar from the sleeve cap, then 1 bar from the armhole, two times, then 1 bar from the sleeve cap and 2 bars from the armhole once. Keep repeating this sequence until you reach the stair step bind off stitches.

Since the first and last stitches become absorbed into the seam, you can see how important it is to form the SSK and K2TOG decreases neatly, since they form a very visible line along the diagonal portion of the sleeve cap. Once the diagonal slant is finished, you'll reach stair steps again. Seam these using the horizontal method, making sure we go into the center of the v of each stitch, avoiding the gap between rows. At the center of the underarm remove the needle leaving the left-over yarn to be woven into the seam once finished. Return to the top, pin front of sleeve cap to armhole, rethread the tapestry needle with the other half of the yarn. The yarn comes out of the back of the stitch on the sleeve cap, so from back to front, come out through the center of the V of the stitch next to it. Then seam the front like the back.

Once seamed, the sleeve should lie flat around the circumference of the armhole. Neither the sleeve nor armhole should pucker or stretch. When using the Mattress stitch, pull seaming thread taut every inch or two. Holding both pieces at once, stretch the seam out to make sure you haven’t pulled the seaming thread so tight that it draws up the fabric. Remeasure your armhole to make sure the length matches the schematic after you’ve finished seaming before weaving in ends. Take a step back and look at the overall pieces a couple of times as you’re seaming. Make sure they look even and are coming together the way you like. As you seam, remove the pins and work one small section at a time to keep each piece ending at the same spot.

A sleeve cap is not designed to be flat. You may find that seaming flows better when you let the sleeve cap rest over your fist as you seam. Keep turning it as you go and let the rounded, fullness of the cap take shape as you work. Photos in this article are from Talbot Cardigan

Yarn is Hazel Knits, Lively DK, in color Sweet and Sour.


Hiatt, June Hemmons. The Principles of Knitting. New York, NY: Simon & Schuster, 1988.

Holladay, Arenda. “Seams – Part 3” Cast On Magazine Feb-Apr 2009.

Newton, Deborah. Finishing School, Master Class for Knitters. New York, NY: Sixth & Spring Books, 2011.

Stanley, Montse. The Handknitter’s Handbook. Newton Abbot, Devon: David & Charles Publishers, Inc. 1986. Distributed in US (New York, NY) by Sterling Publishing Co, Inc.

Vogue Magazine Editors. Vogue Knitting. New York, NY: Sixth & Spring Books, 2002.

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