The project we're working on has an edging on just one edge. But, what if one wants to put an edging all around.......
Here's an example of this -- a blanket with a single crochet edging.
To make it easier to add a crocheted edging, I used a chain stitch selvage when knitting-- I.e., I knitted the last stitch of every row and slipped the first stitch of every row purlwise with yarn in front -- on both right and wrong side rows.
To make the single crochet edging: Start with a single loop on the hook, just as you did when starting the edge for the terry towel dish towel. Single crochet around. This time there is no need to make any chain stitches. I used a size 10 needle for the knitting part and a size H crochet hook for the crochet part. Make 1 single crochet under each (double) loop of the chain stitch selvage and 1 single crochet under the bottom/top of each stitch from the cast on/bind off edge. To turn the corner, single crochet 3 times in the same place. The picture shows a corner with the extra stitches (to make it lay flat) and a sc in process of being created.
When you get back to the first stitch worked, you need a way to join the edge together. The answer is the slip stitch. It's almost invisible.
Most stitches are worked by slipping the hook under both loops at the top of a stitch (unless you want a ribbed effect). For a slip stitch (slip st), place the hook under the back loop only. Yarn over. Then draw the yarn through both loops. NexStitch has a video of the stitch plus other uses for the slip stitch.
edited March 2008: In England, this stitch is called a single crochet stitch.
Finish off the piece essentially as you would a piece of knitting. Elongate the last loop and snip off the yarn just as in knitting. Then weave it in just as you would for knitting. NexStitch has a video of weaving in the ends. I dislike needles and so use a crochet hook to pull the yarn through.
If this were crocheted back and forth, I would do exactly as the video shows (except for using a hook instead of a needle). Since this is crocheted in the round, I would weave the yarn around the first few stitches made in the round instead of the last few.
Here is the finished piece, not yet blocked. The slip stitch join is in the upper right hand corner. The bottom of the picture shows what the wrong side of a single crochet stitch looks like.
Here is a picture from the American Thread Company booklet describing the slip stitch.