Back Door
The Back Door is the entry point to the inside of a Facility which is located outside of the facilities Courtyard. It is an Infantry-only area, with a door too small for any Vehicles.
The only built-in defense for a Back Door is a simple IFF lock.
However, due to the design of the facility, the back door ("BD") is inherently easy to defend with a small group. The door connects to a long, low-grade sloping interior hallway with 90 or 180 degree bends before opening into the facility's lower levels.
This hallway, when populated with defenders, is impassable via conventional means, although it is sometimes susceptible to the MAX Crash rapid-advance tactic.