The building's corner piers contained the mechanical services (elevators, HVAC, etc.). A dual elevator system was installed, one for use by the public and one for use by staff. A dual set of hallways also existed in portions of the buildings. The smaller set of dual hallways was for public use. The public elevators connected only to the public hallways, isolating the public from FBI workers. Several portions of the public hallway contained glass partitions through which the public could see FBI personnel at work.