It never ceases to surprise me how many people, even in this day and age and with all the publicity around opportunist crime, still leave an open invitation to opportunist thieves.
In a recent case in my area a home was burgled and many valued possessions taken.
It was even more disturbing when I found out that the thieves didn’t even ‘break and enter’ they simply used a key in the back door!
Many house owners tend to fit stylish locks to their front door, all manner of brass and other fancy metals cast or shaped into styles as varied as minimalist to Greco – Roman and in the main they are very secure. These same house owners, like my neighbours, then fit the cheapest and least secure of locks to the rear entrance of the home, the back door.
Many New Zealand houses still have the very simple two lever mortise locks fitted to their back doors. These locks are strong enough and easy to use however they are not very secure, you only need twelve keys and all these locks can be opened!
In the ‘good old days’ this was an excellent situation in that if you ever locked yourself out you could go to a neighbours house on the same estate and borrow their key.
Sadly today this type of lock is begging to be opened by a thief.
Mortise lock.
The best way to over come the problem is to remove this lock and fit a more secure unit such as a five lever lock. 
Mortise locks have two latches, one a spring loaded latch that depresses as the door is closed past the door jamb and then drops into the hole in the striker plate. This then holds the door in place until the door handle is turned which pulls the latch back against the spring and so opens the door. The other latch is the locking bolt operated by the key that will lock the door in place. This ‘bolt’ latch is moved backwards and forwards when the key is able to operate a set sequence of levers. The more the levers the more the combinations and the more secure the lock.
This is why you will see irregular cut shapes on all types of keys; the cuts on the keys match the shapes of the levers in the lock. As its name suggests the mortise lock is fitted into the edge of the door, this makes the lock fairly secure; a much more secure lock is a mortise deadlock.
This unit fits in the same way as the standard mortise lock into the edge of the door. The main difference is that it only has one bolt and that bolt can only be operated by a key and once again the more levers the lock has the more secure it will be.
The one disadvantage of this type of lock is that you will need another type of lock on the door that will simply clip into place (using a spring loaded latch) when the door closes and can be easily open by a lever handle. Otherwise as you come and go through the door, while at home, a key will be needed!
This lock that mounts on the surface of the door should be used for privacy only on interior doors as they offer very little real security. If this is your only means of security on your back door fit a more secure lock immediately!
If you are unsure at all about security, talk to the experts at your local hardware store or locksmith. You don’t need to pay a tradesman a fortune as most locks even the most secure come with excellent fitting instruction and can be fitted by the home handyperson.
Another source of some very good information is your local community policeman, find out who he or she is and have a chat sometime!
Email Chris with any DIY questions and queries you may have.
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