Abstract: The device enables a trim adjustment of the vehicle seat. An upper side of each upper section of a slide member carries two square members having vertical wings. The vertical wings maintain, at their upper ends either frontwardly or rearwardly of the seat, spindles on which is articulated a shoe-square. One of the two square members carries an articulation iron fitting enabling, by means of a reduction lever rotating with the mobile flange of each articulation, to raise a rear or front shoe-square in order that a seat frame fixed on the shoe-squares is displaceable by a clearance angle delimited according to needs either for a rear part of the seat or for a front part of the seat between a lower dead point and an upper dead point.