How to: graft two cast off edges

This is a simple way of sewing up pieces of stocking stitch along the two cast-off edges for a less noticeable seam, as it conceals the top edges with V-shaped stitches.

The seam is finished like a hinge, with the two cast off ends butting up against each other, and the stitching worked across the top. On thicker yarns this can be more noticeable, so this is best used for shoulder seams on lightweight garments.
First, lay your two pieces flat on a surface with the two cast-off edges together, the right sides facing up and columns of stitches aligned. Thread your tapestry needle with matching yarn, and starting with the lower piece by bring it up through the middle of the V of the first clear stitch close to a row end and just below the cast off. Leave a tail long enough to be able to fasten off and weave in after, as the edge stitches may be rolled slightly or even be concealed in other seams.
Insert the needle under both legs of the opposing stitch (that is an upside down V of the upper piece. Take the needle back down the same hole as you started from in the lower piece to make the first new V stitch. Bring your needle up through the middle of the V in the next stitch along on the lower piece, then under the two legs in the piece above. Carry on working across the two pieces, in effect working under two legs of a stitch in each one.
Use the natural gaps within the stitches, rather than splitting them, and make sure your stitches don’t wander and you stick to working along the same row each time.
Ideally your V stitches will be the same size as this your knitted ones, although it may take a few to get into your stride. Check your sewing up every few stitches and tease the yarn along to even up the Vs as need be or until you get into a rhythm. Fasten off each end with a figure-of-eight stitch.