Abstract: A fastener for securing a sink unit in a worktop has a clip (11) for attachment to a rail and a hinged clamping member (12) which is tightened up against the underside of the worktop by a screw (25). This threads through the hinge pin (13), and when undone allows the clamping member to swing back to and stay in an inoperative position where it will clear the edge of the hole of the worktop (19) as the unit (20) is lowered in. Doing up the screw causes the clamping member to swing and project a portion (21) under the worktop. The clamping member has guide fingers (23) which engage diametral slots (24) in the ends of the hinge pin.