The invention relates to an additional lock composed of a geared locking bolt which is displaceable by a cylinder 1 with gear. Said lock is externally placed on the inner side of the door of the space to be secured. The height of the strike plate 7 can be modified with additions 8 for leveling the striking plate 7 and the lock’s body 2 of whatever door. A protective cylinder is optionally provided. Said lock can be breached solely by malicious intervention; its placement is easy while no operational damage caused by the passage of time has been observed.
