Stay tuned for this knitting demonstration video. This three needle bind off technique produces a very neat, flexible shoulder seam – and, no sewing is required. Begin by moving the shoulder stitches from their stitch holders to appropriately sized needles.
I like to use double-point knitting needles for this, but it's not necessary. If you are using regular straight knitting needles, just make sure that, when right sides are placed together, the knitting needles are pointing in the same direction. If you don't have three needles of the same size, and your pattern is knit with size 8's, you could hold the stitches on the 8's and bind off with a 9. Since many knitters have a tendency to bind off too tightly, this will help with that problem as well.
Place the garment pieces right sides together. With a third needle, knit one stitch through the first stitch on both needles. Now repeat, knitting a second stitch through the second stitch on both needles. Pull the first stitch knit over the second stitch, as for a regular bind off, and continue across the row, until all stitches are bound off. You must work with the same number of stitches on each needle.
Hope this knitting instrucional video helps you with your binding off skills.