A long tail cast on is a method of casting on stitches using a length of yarn that is estimated to be about twice the width of the finished knitted piece. To do a long tail cast on, make a slip knot in one end of the yarn and hold it on the needle in your left hand. Make an underhand loop around your left thumb with the working yarn (the yarn leading to the ball) and use your right hand to pull this loop through the slip knot (do not pull tight). You have now made your first stitch! Continue making loops around your thumb and pulling them through until you have the required number of stitches.