A device for locking movable leaves such as window panes and comprising a main lock provided with a catch mounted on the leaf and adapted to cooperate with a box-staple fixed in oppositely facing relation on the casing against which the leaf is brought to bear in the closed position and at least one auxiliary lock. The device comprises a system for the remote operation of the auxiliary lock by the catch of the main lock by means of a mechanical connection system carried by the casing. The connection system according to a specific embodiment comprises a slide-block which is housed within the box-staple, said slide-block being connected to motion-transmission means carried by the casing and terminating in a rocking-latch which forms part of the auxiliary lock.