Locking device for an opening element comprising: - a door fitting intended to be mounted on the opening element connected to a manoeuvring member able to be actuated by a user, said door fitting able to drive at least one bolt-holder rail in longitudinal translation under the effect of the actuating of said manoeuvring member, - at least one hook bolt extending as a protrusion from each bolt-holder rail according to a direction orthogonal to the latter, and integral with the latter in longitudinal translation at least in the direction of its locking, - each bolt-holder rail being adapted to be able to be mounted along an edge of the opening element, and driven in translation along an edge of the opening element according to the longitudinal direction of the bolt-holder rail and of the edge, corresponding to a locking direction of each bolt, - each bolt-holder rail comprising at least one connecting rod and at least one bolt, with each connecting rod and each bolt being adapted so that each bolt can be assembled to a longitudinal end of at least one connecting rod by longitudinally extending the latter beyond said longitudinal end and in such a way that the bolt can be driven in longitudinal translation in one direction and in the other by the connecting rod, - each connecting rod is flexible in bending in such a way as to allow for the mounting of the bolt-holder rail by the introduction of a bolt between the recesses of lateral wings of a profile of the opening element, and longitudinal sliding inside the profile, by curving through bending at least the connecting rod connected to the bolt being introduced, - each longitudinal end of each connecting rod and each bolt being adapted to form conjugated means for assembling the bolt and the longitudinal end of said connecting rod by irreversible press fitting by longitudinal traction. - a door fitting intended to be mounted on the opening element connected to a manoeuvring member able to be actuated by a user, said door fitting able to drive at least one bolt-holder rail in longitudinal translation under the effect of the actuating of said manoeuvring member, - at least one hook bolt extending as a protrusion from each bolt-holder rail according to a direction orthogonal to the latter, and integral with the latter in longitudinal translation at least in the direction of its locking, - each bolt-holder rail being adapted to be able to be mounted along an edge of the opening element, and driven in translation along an edge of the opening element according to the longitudinal direction of the bolt-holder rail and of the edge, corresponding to a locking direction of each bolt, - each bolt-holder rail comprising at least one connecting rod and at least one bolt, with each connecting rod and each bolt being adapted so that each bolt can be assembled to a longitudinal end of at least one connecting rod by longitudinally extending the latter beyond said longitudinal end and in such a way that the bolt can be driven in longitudinal translation in one direction and in the other by the connecting rod, - each connecting rod is flexible in bending in such a way as to allow for the mounting of the bolt-holder rail by the introduction of a bolt between the recesses of lateral wings of a profile of the opening element, and longitudinal sliding inside the profile, by curving through bending at least the connecting rod connected to the bolt being introduced, - each longitudinal end of each connecting rod and each bolt being adapted to form conjugated means for assembling the bolt and the longitudinal end of said connecting rod by irreversible press fitting by longitudinal traction.