The Long Tail Cast On can be made tight if necessary, or very loose as needed, simply by adjusting the size of the needle or needles used during the cast on. If you need a tight, stable cast on edge, use a size or two smaller needle. If you need loose, stretch cast on, use several sizes larger needle. For the cuff of socks or mittens, try double up the needles you’ll be working with to do the cast on. Then pull one needle out of the cast on, and start knitting.
This method only works for starting new work. You can’t use this method to cast on in the middle of work, such as when knitting the thumb hole on a mitten or changing colors in entrelac.
Here is a video demonstration of the Long Tail Cast On.