The Retaining Ring is found on the underside of Ultrafeed^®, Leatherwork^®, Yachtsman, Stitch Master^® and Read's Sewing Machines. This is the component that holds the Shuttle Gib Hook in position. At the top of the ring there is a thin curved metal plate called the Retaining Ring Cap Spring (sold separately). This Cap Spring is secured with two screws (also sold separately).