A locking device (11), e.g. a lock washer, for use with a screw threaded fastener (71), said locking device comprising at least a first disc-like body (12) comprising an annular portion (13) with at least one aperture (15) therein and a central through-hole (14) e.g. a washer having notches (15) open to the outer periphery and at least one further body (25) held in said one aperture (15). The further body may be shim (22) also having a central hole (24) and at least one tab (25) which extends through the notch (15) and has an end portion which juts above adjacent surface of the washer to engage an adjacent surface on the fastener when compressed, on tightening of the fastener deflects within the void of the aperture in which it is located under the influence of the tightening of the engaging surface such that under any tendency to loosen, the tab jams against the opposing surfaces and resist loosening of the fastener.