Lock comprising: - at least one fastening device able to be positioned on a first portion of a window frame adapted to stop up against a second portion of said window frame, provided with at least one sliding element along a substantially vertical sliding direction and with at least one hook associated with said sliding element in an integral manner; - at least one fastening seat able to be associated with said second portion of said window frame and adapted to receive said hook to form a closure coupling; - at least one control device associated with said fastening device to lift/lower said sliding element along said sliding direction for the passage from an opening configuration, in which said hook is disengaged from said fastening seat, and a closure configuration, in which said hook is inserted into said fastening seat; - a locking device able to be associated with at least one of said first portion and said second portion, and operable between a locking configuration, in which it interacts with said hook to prevent said hook from sliding along said sliding direction into said closure configuration, and a passage configuration, in which it is released with respect to said hook to allow it to slide for the automatic passage of said sliding element into said closure configuration; wherein said locking device comprises an interaction body provided with at least one solid portion interacting with said hook in said locking configuration to prevent it from sliding; characterized by the fact that: - said interaction body comprises a hollow portion adjacent to said solid portion and penetrable by said hook in said passage configuration. - at least one fastening device able to be positioned on a first portion of a window frame adapted to stop up against a second portion of said window frame, provided with at least one sliding element along a substantially vertical sliding direction and with at least one hook associated with said sliding element in an integral manner; - at least one fastening seat able to be associated with said second portion of said window frame and adapted to receive said hook to form a closure coupling; - at least one control device associated with said fastening device to lift/lower said sliding element along said sliding direction for the passage from an opening configuration, in which said hook is disengaged from said fastening seat, and a closure configuration, in which said hook is inserted into said fastening seat; - a locking device able to be associated with at least one of said first portion and said second portion, and operable between a locking configuration, in which it interacts with said hook to prevent said hook from sliding along said sliding direction into said closure configuration, and a passage configuration, in which it is released with respect to said hook to allow it to slide for the automatic passage of said sliding element into said closure configuration; wherein said locking device comprises an interaction body provided with at least one solid portion interacting with said hook in said locking configuration to prevent it from sliding; characterized by the fact that: - said interaction body comprises a hollow portion adjacent to said solid portion and penetrable by said hook in said passage configuration. - said interaction body comprises a hollow portion adjacent to said solid portion and penetrable by said hook in said passage configuration.