Window or French window having first and second sashes arranged so as to slide in two sliding directions (I-I) that are parallel to one another, the first and second sashes having a first and a second upright, respectively, extending along a first longitudinal direction (II-II) and a second longitudinal direction (III-III), respectively, said first and second uprights being intended to come into register with one another in order to form a central upright of a window or French window when the first and second sashes are in a closed position in which they have the smallest mutual overlap, said first and second sashes being borne by rolling means that allow them to slide, said window or French window comprising: - at least one elastically compressible seal (12, 13) arranged so as to be interposed between the first and second uprights when the first and second sashes are in the closed position, - a first locking member, borne by the first upright so as to be able to move in a transverse direction (V-V) perpendicular to the first longitudinal direction (II-II) and to the sliding direction (I-I) between a first position closer to the first upright and a second position further away from the first upright, characterized in that: - the rolling means bearing the first and second sashes allow the first and second sashes to move transversely to the sliding direction (I-I), - said window or French window comprises a second locking member borne by the second upright and able to slide along the second upright between a closer position and a further-away position, the second locking member being further away from the first locking member when it is in the further-away position, - the first and second locking members are designed to come into abutment against one another at respective first and second abutment surfaces, which are configured such that: a. the movement of the second locking member towards its closer position, when the first locking member is in the first position, causes the first and second uprights to move closer to one another in the transverse direction (V-V), b. the movement of the first locking member towards its first position, when the second locking member is in the closer position, causes the first and second uprights to move closer to one another in the transverse direction (V-V). - at least one elastically compressible seal (12, 13) arranged so as to be interposed between the first and second uprights when the first and second sashes are in the closed position, - a first locking member, borne by the first upright so as to be able to move in a transverse direction (V-V) perpendicular to the first longitudinal direction (II-II) and to the sliding direction (I-I) between a first position closer to the first upright and a second position further away from the first upright, - the rolling means bearing the first and second sashes allow the first and second sashes to move transversely to the sliding direction (I-I), - said window or French window comprises a second locking member borne by the second upright and able to slide along the second upright between a closer position and a further-away position, the second locking member being further away from the first locking member when it is in the further-away position, - the first and second locking members are designed to come into abutment against one another at respective first and second abutment surfaces, which are configured such that: a. the movement of the second locking member towards its closer position, when the first locking member is in the first position, causes the first and second uprights to move closer to one another in the transverse direction (V-V), b. the movement of the first locking member towards its first position, when the second locking member is in the closer position, causes the first and second uprights to move closer to one another in the transverse direction (V-V). a. the movement of the second locking member towards its closer position, when the first locking member is in the first position, causes the first and second uprights to move closer to one another in the transverse direction (V-V), b. the movement of the first locking member towards its first position, when the second locking member is in the closer position, causes the first and second uprights to move closer to one another in the transverse direction (V-V).