Structure for a motor vehicle door, comprising at least: - a hollow lower box section on an upper edge of which is attached a frame intended to accept a window of the vehicle, - the said frame being equipped with at least one upper guide upright and the box section being equipped with at least one lower guide upright, fixed to the said box section by means of a first fixing element, - the said upper and lower guide uprights being intended for the sliding of the window between an up position in which the window is accepted by the said upper guide upright and a down position in which the window is accepted inside the box section via the lower guide upright, and - means of attachment of a control for opening from the outside, equipped with a lock for actuating the opening and closing of the door, - a second fixing element for fixing the said lower guide upright to the box section, which structure is characterized in that: - the said first fixing element is arranged on a lower part of the said lower guide upright and the said second fixing element is arranged on an upper part of the said lower guide upright, substantially facing the lock of the control for opening from the outside which is installed on the door, and in that - the said second fixing element comprises a plurality of surfaces (27, 28, 29, 30, 31) each acting as functional surface, a planar first functional surface, substantially perpendicular to the said lower guide upright being arranged with respect to the said frame intended to accept the window in such a way as to prevent any object from being inserted between the window and the said box section in order to reach the lock of the control for opening from the outside. - a hollow lower box section on an upper edge of which is attached a frame intended to accept a window of the vehicle, - the said frame being equipped with at least one upper guide upright and the box section being equipped with at least one lower guide upright, fixed to the said box section by means of a first fixing element, - the said upper and lower guide uprights being intended for the sliding of the window between an up position in which the window is accepted by the said upper guide upright and a down position in which the window is accepted inside the box section via the lower guide upright, and - means of attachment of a control for opening from the outside, equipped with a lock for actuating the opening and closing of the door, - a second fixing element for fixing the said lower guide upright to the box section, which structure is characterized in that: - the said first fixing element is arranged on a lower part of the said lower guide upright and the said second fixing element is arranged on an upper part of the said lower guide upright, substantially facing the lock of the control for opening from the outside which is installed on the door, and in that - the said second fixing element comprises a plurality of surfaces (27, 28, 29, 30, 31) each acting as functional surface, a planar first functional surface, substantially perpendicular to the said lower guide upright being arranged with respect to the said frame intended to accept the window in such a way as to prevent any object from being inserted between the window and the said box section in order to reach the lock of the control for opening from the outside. - the said first fixing element is arranged on a lower part of the said lower guide upright and the said second fixing element is arranged on an upper part of the said lower guide upright, substantially facing the lock of the control for opening from the outside which is installed on the door, and in that - the said second fixing element comprises a plurality of surfaces (27, 28, 29, 30, 31) each acting as functional surface, a planar first functional surface, substantially perpendicular to the said lower guide upright being arranged with respect to the said frame intended to accept the window in such a way as to prevent any object from being inserted between the window and the said box section in order to reach the lock of the control for opening from the outside.