This cast on requires three lengths of yarn and leaves behind a picot edging. This is creating by alternately pulling up loops through the doubled yarn and completing yarn overs with the single strand.
Grasp the three yarn tails and the needle in your right hand.
Using your left hand, split the yarn so that one strand passes over your index finger and the other two strand pass over your thumb. This is quite similar to the positioning for the Long Tail Cast On.
*Wrap the two strands of yarn around your thumb twice in a counter-clockwise motion.
Insert the needle under the strands that are wrapped around your thumb.
Pass the needle over the top of the single strand of yarn from your index finger and draw a loop through all of the strands on your thumb.
Tug on the three strands of yarn with your left hand to snug them up.
Pass the needle over the top of the index finger strand from front to back to create a yarn over.
Repeat from * until you have the desired number of stitches cast on. After a few rows of knitting, you will see the decorative edge that the cast on has created.