Instructables user stinkymum made this knitting tutorial for the Instructables Craft Skills Contest: How to knit a “Picot” Edge:

Most sweaters, hats etc. have a ribbed edge, which stops the knitted piece from curling up. It is also stretchy. If you don’t want a stretchy hem or sleeve cuff there is an alternative. It is called the “picot” edge. Here is how to achieve it.