Easy unlocking of any MS Deadlock by approximately 3 lbs. downward force on a 3 In. lever. Lever is spring loaded to horizontal, relocks with upward motion. Indicator signals lock status. Can be installed in place of existing key cylinder or cylinder type thumbturn on inside of door. 4550 Deadlock Lever not compatible with 7/8 In. backset locks. Turn lever downward 90 Deg. to unlock. When released, lever returns to horizontal. Turn lever upward 90 Deg. to relock. Key operation from outside is not affected. Clutching action prevents damage to internal components. compatible with any MS pivoted bolt deadlock including “Schoolhouse” versions can be fitted with the 4550 including MS1850S, MS1950, MS1837, etc. Derivative units such as 1870, 1870HM, or 1877 flushbolts (bolt into threshold) are also operable by the 4550 lever. Not compatible with MS+1890 or 2190 Deadlock/Latch or with 7/8 In. backset locks. Individually boxed with installation instructions, mounting screws, and drive pins for both single point and threshold bolt-equipped locks.