Abstract: A locking device is described which is self-adjusting in length and it is therefore adapted to compensate possible differences in the distance between the points of mutual fastening of two bodies.The device of this invention includes a first and a second member, one of them being integral with one of the bodies to be connected, while the second is non-rotatably slidable within the first member, and is biased to partially project out of the latter, by a spring interposed between the first and the second members. The spring keeping the second member abutting against a fastening portion of the second body. The device includes a fastener for mutual fastening of the first to the second member, and to the fastening portion of the second body.