When joining the top of a sleeve to the body of a sweater, I like to use a combination of both mattress stitch and grafting. Grafting is used for the edge with the bound-off stitches, while mattress stitch is used on the selvedge stitches. This provides an almost invisible seam. That’s not quite accurate, the stitches on the sleeve do show, but they look like the last row of knitting so it’s important to use the same yarn as the sleeves.
I use this technique any time I’m joining two pieces perpendicularly; that is, attaching a cast-on or bound-off edge to the side edges or selvedge of another piece.
I generally determine how many stitches there are on the sleeve top and how many rows there are along the selvedge edge. I look at the v-shaped stitches along the bound off edge as if they are traveling from the top down. Each “V” represents one stitch (they are upside-down Vs in the following photo). Each bar along the selvedge represents one row. For my gauge, I often find the ratio is five stitches to seven rows.
In the case of my sleeve I have 60 stitches and 84 rows. Each number divides evenly by 12 giving a ratio of 5:7. I’ll seam the pieces together in groups of five stitches as follows:
stitch 1 >> row 1
stitch 2 >> rows 2 & 3
stitch 3 >> row 4
stitch 4 > row 5
stitch 5 > rows 6 & 7
Insert the needle under one or two of the bars (depending on the pattern/grouping you’ve established) between the selvedge stitch and the next column of stitches. This is just like the mattress stitch described in the last post.
Graft the sleeve top by inserting the needle underneath the inverted v-shape just below the bind-off edge.
Repeat Steps 2 and 3, pulling the yarn through gently and maintaining the knitted tension.
If you don’t get a nice even ratio and have a few left-over rows (which is often the case) then pick up an extra bar (Step 2) every now and then as you go along sprinkling the extra rows evenly along the seam.