Fastening device

A connecting part (3) couples to an object (2). An immobilizing part (5) ensures safe fastening of the connecting part on the object, which is characterized by the fact that the connecting part includes a clamping part (4) to lead through an opening in the object and the immobilizing part locks into the clamping part, in order to prevent the clamping part from being detached from the opening. An independent claim is also included for a casing for an electronic control unit incorporating a fastening device.