Movable assembly for a cut-off mechanism of a motor vehicle headlamp, the movable assembly comprising at least one movable device and a cut-off bar suitable for fitting to a support element of the movable device, said support element comprising at least one housing (10A, 10B), said cut-off bar being provided with at least one attachment foot (11A, 11B), said housing (10A, 10B) and said attachment foot (11A, 11B) cooperating and being configured to allow a fitted position to be obtained in which the attachment foot (11A, 11B) is inserted in the housing (10A, 10B), following insertion by pressure, so that the cut-off bar can be attached removably to the movable device, characterised in that the cooperating housing (10A, 10B) and attachment foot (11A, 11B) have a shape and dimensions adapted respectively to produce at least some 'lateral' contacts (L1A, L2A, L1B, L2B) in the fitted position, the adjective lateral applying to the sides (C1, C2) of the width of the elongate attachment foot (11A, 11B), on both sides of a longitudinal axis of the attachment foot (11A, 11B), said attachment foot (11A, 11B) having a generally planar elongate form, the length of the attachment foot (11A, 11B) along a longitudinal axis and the depth of the housing (10A, 10B) being adapted to one another to obtain a given positioning of the cut-off bar on the movable device, during contact (PA, PB) of the free longitudinal end of the attachment foot (11A, 11B) against the bottom of the housing (10A, 10B), said attachment foot (11A, 11B) comprising at least one transverse bead configured to come in contact with a wall of the cooperating housing, the adjective transverse applying to the sides of the thickness of the attachment foot (11A, 11B). said support element comprising at least one housing (10A, 10B), said cut-off bar being provided with at least one attachment foot (11A, 11B), said housing (10A, 10B) and said attachment foot (11A, 11B) cooperating and being configured to allow a fitted position to be obtained in which the attachment foot (11A, 11B) is inserted in the housing (10A, 10B), following insertion by pressure, so that the cut-off bar can be attached removably to the movable device, characterised in that the cooperating housing (10A, 10B) and attachment foot (11A, 11B) have a shape and dimensions adapted respectively to produce at least some 'lateral' contacts (L1A, L2A, L1B, L2B) in the fitted position, the adjective lateral applying to the sides (C1, C2) of the width of the elongate attachment foot (11A, 11B), on both sides of a longitudinal axis of the attachment foot (11A, 11B), said attachment foot (11A, 11B) having a generally planar elongate form, the length of the attachment foot (11A, 11B) along a longitudinal axis and the depth of the housing (10A, 10B) being adapted to one another to obtain a given positioning of the cut-off bar on the movable device, during contact (PA, PB) of the free longitudinal end of the attachment foot (11A, 11B) against the bottom of the housing (10A, 10B), said attachment foot (11A, 11B) comprising at least one transverse bead configured to come in contact with a wall of the cooperating housing, the adjective transverse applying to the sides of the thickness of the attachment foot (11A, 11B).