The plunger lock on top drawer is standard. Additional plunger lock(s) can only be used as a dual control option along with the use of a plunger lock on the top drawer of the cabinet. Dual control locking options require both locks to be engaged or disengaged before securing or allowing access to any drawer. Independent control locking option allows for drawers that are secured and accessed independently of the other(s). When a combination lock or Medeco key lock is installed on the top drawer of a file, it replaces the standard plunger lock