A locking mechanism for locking fitting joinery, this locking mechanism comprising: - at least one nut mounted rotating in a housing and cooperating with at least one locking member and/or a transmission member, such as a trestle, a maneuvering rod, a drive pinion, to push this locking member and/or this transmission member back between a position, in particular a locked position, and at least one unlocked position, by rotation of said nut along a given travel (18a, 18b) between two angularly offset extreme positions (19a, 20a; 19a, 20b); - stop means capable of occupying, on the one hand, a first position in which they cooperate with the nut in order to allow the rotation of the latter over a first angular travel and, on the other hand, at least one second position in which these stop means allow the rotation of said nut according to a second angular travel differing from the first angular travel, depending on the case, by its amplitude and/or by at least one of the extreme positions (19a, 20a; 19a, 20b), these stop means comprising a first stop member, on the one hand, mounted in the housing movably between said first position and said second position and, on the other hand, cooperating with complementary stop members (26a, 26b), with which the nut is provided; - in combination with the means for selecting the position (22, 23) of said stop means; - characterized by the fact that the complementary stop members (26a, 26b) assume the form of crown sectors (28a, 28b) axially offset on the periphery of the hub of the nut and the first stop member is mounted movably in the housing, between at least the first position and the second position, and in a direction coaxial to the nut. - at least one nut mounted rotating in a housing and cooperating with at least one locking member and/or a transmission member, such as a trestle, a maneuvering rod, a drive pinion, to push this locking member and/or this transmission member back between a position, in particular a locked position, and at least one unlocked position, by rotation of said nut along a given travel (18a, 18b) between two angularly offset extreme positions (19a, 20a; 19a, 20b); - stop means capable of occupying, on the one hand, a first position in which they cooperate with the nut in order to allow the rotation of the latter over a first angular travel and, on the other hand, at least one second position in which these stop means allow the rotation of said nut according to a second angular travel differing from the first angular travel, depending on the case, by its amplitude and/or by at least one of the extreme positions (19a, 20a; 19a, 20b), these stop means comprising a first stop member, on the one hand, mounted in the housing movably between said first position and said second position and, on the other hand, cooperating with complementary stop members (26a, 26b), with which the nut is provided; - in combination with the means for selecting the position (22, 23) of said stop means; - characterized by the fact that the complementary stop members (26a, 26b) assume the form of crown sectors (28a, 28b) axially offset on the periphery of the hub of the nut and the first stop member is mounted movably in the housing, between at least the first position and the second position, and in a direction coaxial to the nut.