Police and Fire Department advocate "Dead-Locks" on all exterior doors Attractive, surface mounted top security dead locks, ideal for most sliding and hinged doors in either the home or the work place. 

The effect of a dead-lock is that if a criminal does manage to get into your home or business, they won't be able to just open the front or back door and walk out with your property, because they won't be able to unlock the door without they key!