There comes a time in every person’s life when we have to get the door locks changed. Perhaps it jams when you try to unlock it, maybe you’ve lost your keys or – even worse – someone has broken in.

The good news is that changing a lock is something that everyone can do – you needn’t call out a locksmith, which can be costly.

The first step is to measure the size of the locking cylinder. To do that, you’ll need to open the door and measure the distance between the middle of the lock and the outer edge of the door fittings.

Doors are rarely identical on both sides, so often, you’ll need a lock that has sides of different lengths. One common size is a 40/30 double cylinder, for example.

You should be able to pick up a lock cylinder – including the key – at your local hardware store. Keep an eye out for any models that have any official security certification against break-ins.

You’ll need to know if the door should be locked with a key from either side or just from the outside – i.e. whether you need a double or single cylinder lock.

The only tool you’ll need when you install your new lock is a screwdriver. Remove the set screw in the door rebate. Then pull the old lock cylinder out of the lock.

If it’s jammed, try inserting the key and turning it slightly. The cylinder should then come loose.

Next, insert the new lock. Before you fix it again with the set screw, check with the key whether you can easily open and close it.

When it comes to protection from burglary, it helps to know that there are five classes of embedded locks, known as mortice locks – the higher, the better. So if you’re getting a front door lock, go for class four at least. – dpa