There is a glitch with the steel rack. Pick up the steel rack outside the Security Room and carry it back inside. Any main story survivor such as Brad or Otis Frank can push around with the rack. Simply talk to the one you wish to move, such as Otis, and when he is talking, press down on the directional pad to drop the rack. It will tip over into the survivor as long as you are facing them, and push them back. They have to be talking to you for this to work, and Otis will usually try to walk back to his old spot if you don't keep moving him.