Standard Door Knob Locks
Every exterior door should have a knob lock with a bolt that extends from the door knob into the door frames strike plate. The strike plate is mounted into or onto the door frame. Door knob locks are usually selected by the homes builder or contractor. Contractors are of course not "lock experts" and the selection is often based on price. The homeowner can make a much better selection knowing what features to look for and what options are available. In addition, all exterior doors should have a deadbolt. Deadbolts are available as separate units or can be incorporated in a combination with the door knob lock.

The American National Standards Institute (ANSI) has requirements, developed and maintained by The Builders Hardware Manufacturers Association (BHMA). When replacing exterior door locks, use ANSI Grade 1 locks.

For convenience, knob locks can be matched to open with the same key as dead bolts and locks on other exterior doors, eliminating the need to carry and keep track of multiple entry keys. Knob locks are also available with combination locks.
 

Dead Bolt lock. Photo courtesy Masterlock.
 

Dead Bolts
Dead bolts should extend further into the strike plate than a standard knob bolt. At least 1" is recommended. Longer throws makes it more difficult to gain entry by spreading the doorframe. Standard deadbolts utilize a key to open the lock when entering from outside and open from the inside with a single action turn of a knob, thus preventing any entrapment in the event of an emergency. Burglars, however, can easily gain entry through a locked door, even with a dead bolt, by breaking the glass in a window, reaching in, and simply unlocking the door. Standard deadbolts are therefore only recommended for all solid exterior doors without any glass or mail slots within 36” of the lock. If glass panels must be closer, deadbolts can still be used if the glass is covered with a security film, which prevents breakage.

Double Cylinder Dead Bolt lock. Courtesy Rhodes Lock and Key

Double Cylinder Deadbolt
Homeowners, in an effort to prevent the above listed type of entry, install what's called a “double cylinder deadbolt”. This uses a key on both sides of the door. Unfortunately, when the interior key is not in place the double cylinder deadbolts do not allow quick escape during an emergency. If the internal key is left in place the lock basically functions as a standard deadbolt and provides no additional security.

Captured Key Dead Bolt lock. Photo courtesy MUL-T-LOCK-Online.com

Captured Key Deadbolt
This type of lock is much like a combination between a standard deadbolt and a double cylinder deadbolt. A captured key deadbolt is advertised as a way to prevent a thief from breaking glass within arms reach of the lock and, reaching in to unlock a door while still providing a safe and quick escape for the family during an emergency. On the interior side of the door the deadbolt lock has a thumb turn which can be removed from the lock, leaving only a keyhole. The idea is when no one is home, there is no need to leave the thumb-turn in place. The last person to leave removes the thumb-turn and basically creates a double cylinder deadbolt. This way thieves could not reach in to open the latch. The thumb-turn cannot be removed without having a key to the lock. Therefore, small children cannot remove the thumb-turn key. The thumb-turn can also be used as a house key. It is important that whenever anyone is in the home that the thumb-turn is left in the lock at all times. Otherwise, there will be no escape during a fire or other emergency. In evaluating this type of lock it should be considered that the same results can be obtained with a double sided deadbolt by just leaving the key in place when at home. The problem arises when wanting security while you or your children are at home. In this day and age why would anyone want a criminal to be able to reach in and open a door or have to rely on everyone in the household to remember to leave the interior key in place to be assured a quick exit in an emergency. In my opinion, their are too many things that can go wrong with either the double sided or captured key deadbolt to make either worthwhile.

Automatic Dead Bolt lock. Photo courtesy Masterlock.

Automatic Deadbolt
Many rim latch style deadbolts lock automatically when the door is closed. These are great and offer the additional security of not having to remember to always lock your door. The only problem is you can easily get locked out.

 

Keyless Locks

Fairly new on the market, these locks are an excellent choice and there is no need to worry about losing keys. A simple code opens the lock. This code can be changed from time to time or whenever the code is no longer maintained as a secret. i.e. when household help is terminated. Keyless locks are available on door knob locks, deadbolts and combination deadbolt knob lock sets.

Fingerprint Dead Bolt lock. Photo courtesy Sunneo Biometric Co.

Fingerprint Locks
One step above the keyless lock is the fingerprint controlled lock set. Again a great system with no keys to misplace. The main advantage to a fingerprint door lock system is its convenience. These systems are battery powered and come with a low-battery indicator. This system, as well as the keyless lock, are available with an excellent assortment of security features that make them as secure as a deadbolt but a lot more family friendly.

Key Control
Key control is simply a way of controlling who has copies of keys to the home. There are many burglaries where the entry can be traced back to a key that was somehow obtained by the burglar. Most door keys can be easily copied at any local hardware store. Manufacturers now offer locks that use keys that cannot be copied except by locksmiths or the manufacturer themselves.

Key control locks are more expensive and require some extra effort from the home owner. For example, an additional cost is involved in order to get any replacement keys made. The cost and inconvenience of having to go to a locksmith rather than the local hardware store, is weighed against the added security benefits. Key control locks are available in all style deadbolt locks.

Saw-Resistant Bolts
Some deadbolts come with an internal anti-saw pin. The pin spins freely inside the bolt. When a thief tries to saw through a deadbolt with a hacksaw, the pin spins back and forth with every movement of the saw. This system is not fool proof but makes it more time consuming for a burglar to cut through a lock bolt.

Hardened Cased Steel & Beveled Casings
The outside housing of a lock is called the "casing". Many lock manufacturers make their casings out of hardened steel and many make the casing beveled. The hardened cased steel makes the casing more resilient against impact blows. Beveling the casing makes It difficult to keep a wrench on the lock if a thief attempts to twist the lock free with a pipe wrench.

Anti-Drill Feature
Some determined thieves will actually take the time to drill out a lock. Manufacturers combat this by installing hardened steel chips within the lock. When a drill bit hits these hardened steel chips, the drill bit is destroyed.

Remember, the intruder will select the door that looks easiest to break into and that offers the least chance of being seen. Back doors and Garage doors leading into the house offer an intruder privacy and the ability to safely spend extra time breaking in. Extra thought should go into the security at these locations.

Selecting the right door locks and knowing where to install them is only part of a good security plan for your home. When considering security on exterior doors, the strength of the door and doorframe are just as important as the strength of the door lock.

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