Traditional crochet is worked in rows from right to left. However, the crab stitch is characterized by the fact that it is worked backwards, that is, from left to right. It is also different from regular crocheted stitches because instead of bring yarn around the back and over the top of the hook to yarn over, the yarn is brought around the top to the back to yarn over. Lastly, a longer loop is drawn up when yarning over than in traditional crochet.
When finished, the crab stitch rather closely resembles rope braid, and works best as an edging or finishing for a piece. To try it out, start with a row of single crochets long enough to comfortably work with.
After completing a row of single crochets, do not turn the work around. Ch one (for working room), *insert the hk into the next stitch to the right, and yo and draw up a long lp. Yarn over by hooking the yarn down from the back, and pull through both lps on the hk.* Proceed across the row, repeating between the *s.
This pattern node uses crochet abbreviations.