Abstract: An applicator for installing a retaining ring into an external groove of a workpiece comprises a floor having a slot for receiving a grooved workpiece. A pair of groove locators are rotatably mounted alongside the floor. The groove locators have forwardly converging side edges against which the rings engage as they are being pushed forwardly. Such engagement pushes the locators apart whereby forward free ends of the locators are displaced out of the workpiece groove by an advancing ring. The side edges are arranged to impose relatively small forces tending to close the ring, and to retain the ring in contact with the floor.