A Guide To Security Locks

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More than 2,000,000 home burglaries are reported each year. That translates to a home burglary every 13 seconds. According to FBI statistics, break-ins are the most common threat to the home.

Taking the time to carefully research different locking systems will help increase the level of safety for family members and valuable personal belongings. Talking with a professional locksmith or members of the local law enforcement can objectively help evaluate the existing home security and the best options to improve it. These professionals have seen firsthand which locks are secure and which are vulnerable.

Understanding door security locks

Most locks sold at hardware stores and home centers are graded to standards of the American National Standards Institute (ANSI) and the Builders Hardware Manufacturers Association (BHMA). Product grades can range from Grade 1 through Grade 3. Grade 1 is the highest in terms of function and product integrity. And, Grade 3 is the lowest.

The variety and number of security locks available is complicated at best. Here’s how to determine the best security lock for different applications.

Cylindrical locksets

Cylindrical locksets are often used to secure commercial offices and storerooms. These are also called key-in-knob or key-in-lever locks. A locking cylinder in the center of the doorknob distinguishes these locks as a cylindrical lockset. Some models will have keyways in each of the opposing knobs, requiring a key on either side to lock and unlock them. Others may be locked by simply depressing or rotating a button on the center of the inside knob.

These locks are only suitable for very low-security applications. Rooms secured with these locks may require additional locks to properly protect the room. Cylindrical locksets are easily defeated with a common pipe wrench or large channel lock pliers. They are not suitable for an exterior doorway.

Deadbolt locks

Deadbolts are sometimes referred to as a tubular dead bolt. Deadbolt locks are usually mounted, on the door, above the knob. They differ from a cylindrical lock in the internal locking bolt. When the locking bolt is extended, in the locked position, it projects into the doorframe. It cannot be forced back into the unlocked position by applying pressure to the end of the bolt. A dead-bolt lock can provide an acceptable level of protection for storerooms and other areas where more security is needed.

In installations where windows are near the door, a double-cylinder dead-bolt lock, requiring a key to open from either side, should be installed. Double-cylinder dead-bolt locks should not be used for emergency exit doors, or any door that would be used as an exit during an emergency situation. Instead, plan to eliminate the vulnerability created by nearby windows by adding bars or removing the window.

Mortise locks

Mortise locks are those locks recessed into the edge of the door. Frequently found in older homes, they were a popular lock on front doors until the mid 1950s. Most common varieties of mortised locks will have a doorknob on each side of the door. Front entrance doors often will have an exterior thumb latch rather than a doorknob. Mortise locks can be locked from the inside, by using a thumb turn or a thumb button. They are considered low-security devices largely because they weaken the door structure in the mortised area. This is true even in solid-core wood doors. A mortised lockset may be used in heavy-gauge metal doors, but otherwise they provide a weak security point of entry.

Drop-bolt locks

Drop-bolt locks are auxiliary locks similar to dead bolts. They are sometimes referred to as jimmy-proof locks. Both the drop-bolt lock body and the strike plate employ interlocking leaves physically similar to a door hinge. When engaged, the locking pins in the lock body drop down into holes in the strike plate, securing the locking system. With the lock body and the strike plate interconnected with locking pins, they are essentially a single unit and very difficult to separate.

Knob locks

Knob locks are frequently found in less expensive residential installations for exterior doors. They should always be combined with a deadbolt for the primary source of security for exterior doors. Knob locks will not provide acceptable security on external doors. The locking cylinder in a knob lock is in the knob itself and not inside the door. It can be easily broken off the door with a hammer, or twisted off using pliers or a pipe wrench behind the knob. If knob locks are currently installed on exterior doors, replace them with passage knobs and a secure deadbolt.


Detachable padlocks are typically used with a metal hasp or other specialized hardware. Low-security padlocks, which are sometimes called secondary padlocks, are useful only to deter unauthorized access to an area. They are sometimes found on school lockers or garages and provide only minimal resistance to force. Low-security locks are manufactured with hardened steel shackles. Caution should be taken to avoid confusing these locks with similar brass or bronze locks. A brass or bronze lock does not meet the security requirements of the locks with hardened shackles. High-security padlocks may be used to secure assets with high value or high-level threat. They provide the maximum resistance to unauthorized entry when used with a high-security hasp.

Some industrial and commercial padlocks are manufactured to accept interchangeable cores, which allow a common key system to include a variety of locks. Typically, padlocks, door locks, cabinet locks and electrical key switches can all be operated by the same key system. These cores can be removed with a special key to allow rapid rekeying of a series of locks when an unauthorized user is suspected of having access to the key.

Several variations of combination locks are available as padlocks or as a mounted lock. These are still considered low-security padlocks with combinations that can be fixed or changeable. In higher-security applications, combination locks may be either mechanical or electronic. Entering a particular sequence of numbers will lock or unlock this style of lock. When the correct combination is entered, the lock's bolt is retracted.

Access control and electronic control devices

Access control systems are gaining popularity in modern homes as well as in industrial applications. Most access control locking systems are sophisticated electronic locks. The electric assembly may be positioned on the lock or in proximity of the lock. Electronic locks are usually controlled by other systems. Several of the advantages of electric locks are; keying systems can be added or removed without affecting the lock cylinder. Access control locking systems can keep a count on how many times the lock was accessed and by whom. Some electric lock systems provide the additional option of sending an alarm when being accessed.

Code locks are controlled by passwords. In this configuration, they are essentially electronic locks but add an additional layer of security with access-controlling passwords. Imputing the correct password unlocks the device. They are useful in high security installations or areas requiring complex controlled access. Some code lock systems can require biometric details of an individual.

How to improve the security of any lock

Door jams are the weakest element of an exterior door. Most existing Grade 2 or 3 security locks can be strengthened by simply adding a strike plate, or a deadbolt strike box with longer screws for additional protection against forced entry. A doorjamb reinforcement kit consisting of three or four-inch screws and a heavy-duty strike plate will lock together both the doorframe and the two studs next to it. Other options for entry doors are available at your local hardware store to reinforce key strike points such as hinges, latches and the door edges.

Last Updated: September 23, 2012
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About Bill Washburn William "Bill" Washburn has a BA in advertising from the Art Center College of Design and has taught at the University of Southern California and Northrup University. Writing from a well-connected studio in the rural foothills of the west coast, he is a frequent speaker at local art associations and has published numerous articles discussing periods of art history and the fundamentals of drawing and painting. William is a master gardener who grows his own culinary herbs, organic heirloom vegetables and a variety of fruits. He writes frequently about his gardening experiences on his website Pioneer Dad. He is an accomplished advertising writer, fine art painter, and art director with more than 20 years' experience. 

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