- Locking mechanism for sliding doors and windows which comprises a lock with a lock cylinder having a key hole for the key, said locking mechanism comprises a cylinder pin integrated in said lock, a toggle box, a track, a stopper, a second chamber, an operating latch, a blocking toggle, an operating handle, left and right side faces (17, 17'), a first chamber, a body portion, a third chamber, a fourth chamber and screws (24, 24'), and a key which comprises a key shaft, key head, a bore, an inlet and key teeth, wherein: the lock is inserted in the blocking toggle close to the left side face of said blocking toggle; the operating latch is arranged in order to be displaced together with the blocking toggle; the blocking toggle is arranged in such a way with respect to the toggle box that its longitudinal movement is effected by the displacement of said operating handle; the body portion is attached to the blocking toggle by means of the screws (24, 24'); the third chamber and the fourth chamber in the toggle box are arranged in such a way that they allow the movement of said body portion and of the body portion adjacent part arranged in the blocking toggle; the left and right side faces (17, 17') of the blocking toggle are substantially smooth; characterized in that the lock comprises a tab; the operating handle of said blocking toggle is arranged in order to be extended outwardly in a straight line in the vicinity of said right side face of the blocking toggle; the tab of the lock is partially housed in a first chamber in the blocking toggle and partially housed in a second chamber in the toggle box; the tab is arranged in order to be prevented from displacing in said first chamber; the tab is disposed in order to be displaced in said second chamber; the first chamber, the second chamber and the track present different heights, widths, lengths and shaping and are superimposed; the cylinder pin is arranged to be displaced in the track arranged in the toggle box, when it is aligned with said tab in the unblocking position of said locking mechanism; and the cylinder pin is arranged in order to be abutted against a stopper arranged in the toggle box which is aligned with said track, when the tab is arranged perpendicularly with respect to the cylinder pin in the blocking position of said locking mechanism. the lock is inserted in the blocking toggle close to the left side face of said blocking toggle; the operating latch is arranged in order to be displaced together with the blocking toggle; the blocking toggle is arranged in such a way with respect to the toggle box that its longitudinal movement is effected by the displacement of said operating handle; the body portion is attached to the blocking toggle by means of the screws (24, 24'); the third chamber and the fourth chamber in the toggle box are arranged in such a way that they allow the movement of said body portion and of the body portion adjacent part arranged in the blocking toggle; the left and right side faces (17, 17') of the blocking toggle are substantially smooth; characterized in that the lock comprises a tab; the operating handle of said blocking toggle is arranged in order to be extended outwardly in a straight line in the vicinity of said right side face of the blocking toggle; the tab of the lock is partially housed in a first chamber in the blocking toggle and partially housed in a second chamber in the toggle box; the tab is arranged in order to be prevented from displacing in said first chamber; the tab is disposed in order to be displaced in said second chamber; the first chamber, the second chamber and the track present different heights, widths, lengths and shaping and are superimposed; the cylinder pin is arranged to be displaced in the track arranged in the toggle box, when it is aligned with said tab in the unblocking position of said locking mechanism; and the cylinder pin is arranged in order to be abutted against a stopper arranged in the toggle box which is aligned with said track, when the tab is arranged perpendicularly with respect to the cylinder pin in the blocking position of said locking mechanism.