As the name suggests, mortice locks are concealed locks morticed into the door. They have varying levels of security from two levers up to seven levers.
The number of levers (of which there are commonly seven variations) fitted at random in the lock, generate the number of possible key differs. Put simply, a two lever lock has potentially 49 key options (7 x 7). A seven lever lock has 7 x 7 x 7 x 7 x 7 x 7 x 7 or 823,543 potential key differs. Hence you can see the greater number of levers there are, the less likely it is that someone else will be holding the same key as you.
For convenience similar locks can be keyed alike, or as some people say ‘suited’. This means that any number of locks can be made to work on the same key by simply fitting each lock with the same combination of levers. However, we recommend that in general, no more than six insurance rated five lever external locks keyed alike are fitted to the same property. Internally the number is limitless. Many householders fit a keyed alike lock to every internal door giving them extra security when their property is empty.
We strongly advise that at least one commonly used entrance door is not keyed alike to all the others, usually your front door, since if you loose your keys; you have lost the key to every entrance to your property. Keep your main entrance door on a separate key and for convenience, key all your other external doors alike. Only ever keep the main key on your key ring. This way you will be able to secure that one door with bolts until you have called out the locksmith, coming and going through an alternative door to which you have not lost the key.