A cable needle is a useful item to have on hand if you're planning to knit cables, like the one in the Cabled Headband pattern.
Cable needles are short, straight or slightly curved needles that are used to temporarily hold stitches in order to form the cable. To make a cable, stitches are worked in a different order than normal, making the twist within the fabric that we call a cable.
Cable needles are usually made of metal, plastic or wood. They can be straight, have a bend in the middle or be what's called a U-shape, which is really more like a J shape. Cable needles also come in different thicknesses to work with different weights of yarn.
To use a cable needle, simply slip the number of stitches required to work the cable onto the cable needle. Slip them as if you were purling them so that the stitches will not be twisted when you work them back into the knitting.
Work the number of stitches indicated in the pattern and then work the stitches from the cable needle in the same order you would have worked them had they not been moved. Continue the row as normal.
Cable needles are very helpful when working cables, but they aren't required. If you don't want to buy a cable needle to try a cable knitting project, use a double-pointed needle of the same size as your knitting needles (so the stitches won't slide off easily).