A device for locking a plurality of threads includes a first and a second element each of which is provided with a central opening. The first and second elements cooperate to delimit a labyrinth passage for the threads to be locked. The second element is provided with two surfaces which are on opposite sides with respect to the respective central opening and is provided with two external wings which are united to the surface. The surfaces are united, on one side, with a bottom wall of the same second element from which they emerge, and, on the opposite side, with a corresponding external wing of the second element.