The Manfrotto R190,324 Knob Assembly for Leg Locks on 190/3001N Tripod Family 324 is a thumb screw, a bolt, a spring, and a washer that serves as a replacement assembly for the leg locks of the 190/3001N family of tripods, which comprises the 3001N (3001BN), 190D, 190DB, and 190XDB.