It is recommended that all entrance doors are fitted with a mortice lock. Mortice locks provide greater front, side and back door security by being physically embedded, or "morticed" into the door itself. A mortice lock is therefore less vulnerable to ram or forced attack than a surface mounted lock.
Whenever possible try to fit mortice locks that are certified to BS3621 and which can be identified by the British Standard Kitemark symbol.
Mortice locks are available with a 2, 3 or 5 lever mechanism. The higher the number of "levers" the more difficult the lock is to "pick". For front, side and back doors it is recommended that British Standard 5 lever locks are fitted.
Mortice locks are available in a range of different case sizes. The case size is the measurement between the faceplace and the back of the lock as measured in millimetres (typically 54mm, 67mm or 80mm). The case size measurement therefore denotes the depth of the mortice slot in the door.