Lock unit for doors or windows, comprising: - a first drive member and a second drive member that are movable along respective projecting/retracting (DI, DII) directions with respect to a box body of said lock unit , each of said first drive member and second drive member being suitable for being connected to and moving a respective bolt so as to engage the respective bolt with and disengage the respective bolt from a respective locking seat provided on a wall or on a fixed counterframe, - a control element suitable for coupling with a rotatable handle to move said first drive member and second drive member in said projecting/retracting (D I , D II ) directions, - transmitting means (T) for transmitting a movement of said control element to said first member and a second member to drive the bolts, said transmitting means (T) being configured for transforming a control element rotation into a linear movement of said first drive member and second drive member in said projecting/retracting (D I , D II ) directions, - a seat shaped for housing a lock cylinder (C) for key locking said lock unit , - a control device (W) that is activatable by said lock cylinder (C) and configured for enabling the rotation of said handle in a first rotation direction only as far as said lock cylinder (C) is taken, by the respective key (K), in a first angular position, on the other hand preventing , in this first angular position of the key (K), the rotation of said handle in a second rotation direction opposite said first rotation direction, - said control device (W) being configured for enabling the rotation of said handle in said second rotation direction only as far as said lock cylinder (C) is taken, by the respective key (K), to a second angular position, preventing, in this second angular position of said key (K), the rotation of said handle in the first rotation direction. - a first drive member and a second drive member that are movable along respective projecting/retracting (DI, DII) directions with respect to a box body of said lock unit , each of said first drive member and second drive member being suitable for being connected to and moving a respective bolt so as to engage the respective bolt with and disengage the respective bolt from a respective locking seat provided on a wall or on a fixed counterframe, - a control element suitable for coupling with a rotatable handle to move said first drive member and second drive member in said projecting/retracting (D I , D II ) directions, - transmitting means (T) for transmitting a movement of said control element to said first member and a second member to drive the bolts, said transmitting means (T) being configured for transforming a control element rotation into a linear movement of said first drive member and second drive member in said projecting/retracting (D I , D II ) directions, - a seat shaped for housing a lock cylinder (C) for key locking said lock unit , - a control device (W) that is activatable by said lock cylinder (C) and configured for enabling the rotation of said handle in a first rotation direction only as far as said lock cylinder (C) is taken, by the respective key (K), in a first angular position, on the other hand preventing , in this first angular position of the key (K), the rotation of said handle in a second rotation direction opposite said first rotation direction, - said control device (W) being configured for enabling the rotation of said handle in said second rotation direction only as far as said lock cylinder (C) is taken, by the respective key (K), to a second angular position, preventing, in this second angular position of said key (K), the rotation of said handle in the first rotation direction. <EOS>