Let me say right now that I love knitting on edgings. I don't know why, it is such a particularly satisfying maneuver for me to work. It just is. Let me also say at the beginning that if you have never knit on an edging before it is likely to take more yarn and more time than you anticipate (especially true for a wide lace piece). For a simple narrow one, like the one I used on the Scrap Shawl, the process just rolls right along.
For demonstration purposes, we will pretend that this is the body of the shawl, worked to full size. I have just finished the last (Wrong Side) row, and have turned it, as if I were ready to start a Right Side row. But instead of knitting away,
I cast on the number of stitches needed for the edging (in this case, five). Most of the time, I just continue with the working yarn from the shawl body, but I'm using a different color here to make the pictures clearer. In either case, I am now ready to work the first row of the edging pattern. I think of the first and all odd numbered rows as "incoming" rows, because they are working in toward the body of the shawl.
I work up to the last of the edging stitches. Then I work a decrease that uses the last edging stitch and the first of the waiting shawl body stitches. This does two things. It joins the edging to the body, and it uses up (in effect binds off), one body stitch. You could just k2tog, but I like the look better when I do this:
Sl 1 (the last edging stitch)
K1 (the first body stitch)
psso (pass slipped stitch over)
Then, as I have come to the end of the row (as far as the edging is concerned) I turn everything and work the second (outgoing) row.
Now I will turn and work the third (incoming) row, working the join again on the last edging and first body stitches. And so on, and so on.
Every two rows of the edging pattern worked will use up one more stitch from the body.
The edging pattern I used goes like this
Row 1 (incoming): k4, sl 1, k1, psso
Row 2: k5
Row 3: k1, yo twice, k3, sl 1, k1, psso (seven edging sts)
Row 4: k4, k into the first wrap of the yo, p into the second wrap of the yo, k1
Row 5: Bind off 2, k3, sl 1, k1, psso (five edging sts)
Row 6: k5
Now on a fine lace shawl, one would want to calculate the number of body stitches to be used up and the number of edging row repeats and make sure that the whole thing worked out symmetrically - especially if the each edging repeat had many more rows. But this was a very casual project, so I just fudged it. I did work in a little extra ease for the edging on either side of the point of the shawl, by working a couple of the incoming rows without a join. Just knit the last stitch instead of doing the sl 1, k1, psso; turn and work outward.