A method and apparatus for clamping a knife. The invention also relates to a process the preparation of a pyrazolopyran of the formula I, to compositions comprising said compound and processes for the preparation of these compositions. The retractable lifeline further includes a lock assembly to prevent rotation of said drum, and hence extension or retraction of said lanyard, when said lanyard is at a desired length, and an override of the lock mechanism in case of a fall so that the retractable internal shock absorption and clutch mechanism can arrest the fall.