Abstract: The invention relates to a device (1) comprising an assembling piece (3) provided with a hole (4), and a fixing element (5) having a shank (6) as well as head (7). The device (1) has a locking screw (8a) of the head (7), characterized in that the hole (4) is shaped for producing a stop (9) for the head and for enabling the head (7), when it rests against the stop (9), to be displaced inside the hole (4) in the plane of the cross-section of the hole (4), the hole (4) having an inside thread in which the locking screw (8A) is to be screwed so that the locking screw (8A) rests against the head (7) and thus presses the latter against the stop (9). The invention also relates to fixing devices, in particular, surgical implants.