A fastening device has a first fastening member with a plurality of teeth and a second fastening member with a plurality of sockets which are sequentially engagable in tooth and socket pairs in an engagement direction by relative rotation of the tooth and socket. Each tooth has a first surface and a second surface fixed relative to the first surface. Each socket has a recess defined by a first wall and second wall fixed relative to the first wall. Upon engagement, the first and second surfaces of the tooth abut the respective first and second walls of the recess and prevent relative movement of the tooth in the engagement direction and a portion of the first wall of the socket closely abutting the first surface of the tooth is disposed between the tooth and a portion of the first fastening member and prevents relative separation of the tooth and socket.