The crab stitch got its name from the direction in which we crochet it. We do this in the opposite way of basic crochet, that is not from right to left but from left to right. It’s a decorative stitch thanks to which we achieve an effect of diagonal ribbing. For example, it’s very useful for finishing crochet projects.
We begin crab stitches from the end of the row. We make one chain stitch, and then insert the hook in the stitch on the right hand side. We crochet. Now we have two stitches on the hook. We crochet two stitches together and get the first crab stitch. We continue, inserting the hook into subsequent stitches on the right hand side.