Leaving your door unlocked can be an open invitation to a burglar, but sometimes even a locked door won't stop a burglar who's determined enough. If the lock on your doorknob just doesn't seem secure enough, you might want to consider installing a rim lock.
What's a Rim Lock?
A rim lock, or rim latch, is a lock you can mount on the outer surface of your door. Since it's usually used in addition to other, internal locks, it's often called an auxiliary lock. Rim locks, like most other locks, consist of a lock body mechanism (the bit you attach to the door) and a strike (the bit on the doorframe that the latch clicks into). Depending on your security needs, there are several different types you can choose from.
Types of Rim Locks
The basic rim night latch lock attaches to the inside of the door and locks automatically when the door closes. This is a spring-loaded rim lock, which means that the latch opens from the inside via a little knob that you turn and hold while opening the door (much like a doorknob). From the outside, of course, your key does the same thing. Unfortunately, so could a credit card or a file-so you may want to get a deadlock night latch instead. This type of rim latch is also spring-loaded, but it has a secondary latch that deadlocks for added security and can only be opened, both inside and outside, with a key.
If that's not secure enough, you can get a regular rim deadlock latch, which is more like a standard deadbolt. This type of lock is not spring-loaded, so it won't lock automatically like the rim and deadlock night latches, but as long as you remember to lock it with the key when you go in or out, it offers stronger protection against housebreakers.
Of course, a housebreaker with a crowbar and enough patience would probably manage to pry even these locks off your door, so if you're expecting more stubborn burglars, your best bet is a jimmy-proof lock. Jimmy-proof locks usually look like interlaced fingers-the lock body itself latches directly into the strike, where a deadbolt then holds it firmly in place. Since the two sides of the lock itself are connected, it's harder for a burglar to pry either side out of the door.
Installing Your Rim Lock
Once you've decided which rim lock you want, the next step is installation. To install the rim lock, first line up the lock body cylinder on the door where you want it to be and mark the spots for the screw holes and for the cylinder itself. Then, drill or cut holes in the door accordingly, fit the cylinder into the door, and screw it in tightly to the plate on the other side. (If it's not tight enough, a burglar can twist the cylinder in the door and break the screws, and the lock is useless.)
Once the lock body is securely installed, line up the strike on the doorframe opposite the lock, mark screw holes, and drill them. (You may also need to chisel out space for the strike body if it isn't flat.) Then, just screw the strike in place, test the lock, and make adjustments as necessary.
As we said before, rim locks are most effective when used in addition to your regular door locks-so even after you've installed a quality rim lock, don't forget to fasten your other locks, too. With the extra security of a rim lock, however, you can rest a little easier knowing that your home and your belongings are that much safer.