Ball Winder
A ball winder rolls yarn from a hank or loose skein into a loose, center-pull ball that is easier to knit from without the yarn tangling.
Explanation
A ball winder is a mechanical tool that winds yarn, often from a hank held by a yarn swift, into a loose, cylindrical ball with a hole through the center. Because the yarn pulls from the center of the ball rather than the outside, the ball spins in place on the table as you knit, instead of rolling away or tangling the way loose hanks easily do. Ball winders are often used together with a yarn swift to make the process of winding freshly purchased yarn faster and more efficient than winding by hand.