The lock you have on your door is probably a lever lock or a cylinder lock. Both these locks offer different security levels. Lever locks are supplied in a number of variants - 2 lever, 3 lever, 4 lever and even 5 lever. All these lever locks range from low to high security.
A 2 lever lock offers key differs between 18 and 20. This means that lock manufacturers make 20 different keys before they can start the process to duplicate the same 20 keys. Less key differs increase the risk of possible key duplicates that may be nearby – think of a townhouse complex with 100 homes, if the builders used 2 lever locks on the front door, every fifth house would use the same key! Also, the fewer the levers, the lower the security as the lock might be easier to pick.
A 2 lever lock will be most suitable for your internal doors such as bathroom and bedroom doors, where high security is not a priority. A 5 lever lock will offer about 500 key differs, which decreases the probability of a duplicate key being nearby. 5 lever locks are good for your external doors such as front doors and gates. The 5 Lever Mortice Lock from Yale offers 500 key differs and features an anti-saw deadbolt with hardened roller pins. This lock is SABS approved and is good for your external doors.