Most know this, but in each elevatorbay, the farthest elevator back is also a freight elevator and has its own call buttons (located high up on the left side of the door). Handy if there is a crowd.
If you're leaving at 6:00 trying to beat the locking on Jackson, the guard locks left to right, go to the door right of the guard. You can't use the one they're locking or have locked. Accept defeat.