A Buttonhole Edge is sometimes decorated with a little picot. There are many ways to make a picot, and here is one, using the Bullion Stitch.

Star as with a normal Buttonhole Stitch. Wrap the thread several times around the needle (Step 1). Pull the wraps taut around the needle, and, holding the wraps in place with your thumb, pull the needle through the wraps. Finish the Buttonhole Stitch (Step 2).