The retainer has a number of elastic grips (10) positioned around the hole (15) for the screw fastener, with the inside tips of the grips on a circle with a smaller diameter than the shank of the fastener. The grips are claw shaped and are mounted on a collar fastened to the fitting. The claw grips are shaped to clip over the head of the screw fastener when screwed completely home. This ensures a retainer grip even with a reduction in the elasticity of the grips. The grips and the support collar are moulded plastics.
