The cable cast-on provides a somewhat flexible decorative edging at the start of a piece.
To begin the cable cast-on, get two loops onto the left needle using any other cast-on technique (such as simple cast-on). Insert the right needle between these two stitches, and loop the yarn and bring it through as if making a knit stitch. Transfer this new stitch from the right needle to the left needle. Repeat the process, always inserting the right needle between the last two stitches on the left, until all stitches have been cast on.