A device includes first and second inter-engageable parts, each having a longitudinal axis and a connecting face extending substantially transversely to the longitudinal axis. The first part has an engagement formation extending substantially axially and the second part has a receiving formation extending substantially axially, and in which the engagement formation is receivable. The engagement and receiving formations each includes a substantially helicoidal surface extending at least partially around the longitudinal axis of the respective part of the connector, so that rotation of the parts relative to one another about the longitudinal axes, when the parts are substantially co-axially aligned, so that the connecting faces of the parts face one another in a substantially axial direction, causes engagement of the engagement formation with the corresponding receiving formation.