Abstract: A device for attaching a retaining member (1) for an optical apparatus (2) to a support (3) includes a screw (11) for securing the retaining member (1) to the support (3) and having a conical head (13) countersunk in the retaining part of retaining member, and a key connection (12) for aligning the retaining member (1) with the support (3) and secured in place by the screw (11).