An anchor for fixing a first member (35) to a second member (8), such as a plasterboard or similar sheet material wall. The anchor is formed from a plastics material and includes an elongate shank (2) for passage through the second member (8) from a front surface (7) thereof to beyond the rear surface. The shank has a screw thread (17) for engaging the second member for retaining the shank therein, and the shank includes a passage (25) extending from an outer head end (3) for reception of a fastening screw (24-26), a toggle bar (5) and at least one frangible connector (20-21-22) attaching the toggle bar on the shank in an inoperative position at which the toggle bar extends in the longitudinal direction of the elongate shank and does not interfere with passage of the shank through the second member. The toggle bar includes a ramp surface (27) which is contactable by the fastening screw inserted through the passage (25) for moving the toggle bar from its inoperative position to an operative position at which it extends transversely to the longitudinal axis of the shank rearwardly of the rear surface of the second member. The toggle bar in its operative position includes a through hole (23) which is engageable by the fastening screw, whereby a first member (35) associated with the fastening screw is fixable to the second member (8) upon relative rotation of the fastening screw in the shank to draw the toggle bar into engagement with the rear surface of the second member.