Web Exclusive: Locks 101

By April Dalton-Noblitt

With increased interest on safety, many facility professionals are more involved in the details of their organizations’ security systems. While much discussion will be on topics such as funding, lockdowns, and other security and safety issues, one thing remains constant. Access control, in whatever its form, begins with locks. And this subject has its own nomenclature, which can be confusing. Thus, welcome to the world of mortise, strikes, fail safe, and fail secure.Multi-colored locks of love.

There are two types of strikes—mechanical and electronic. A mechanical strike plate is a metal plate affixed to a door jamb with one or more holes for the bolt of the door. When the door is closed, the bolt extends into the hole in the strike plate and holds the door closed.

An electronic strike does the same except that its surface can, upon command, pivot out of the way of the latch, letting the door be pushed open from the outside without any operation of the knob or lever. While activated, the knob or lever can be turned to allow one to leave from a secured area. Thus, an electronic strike gives more flexibility. Lockdowns are faster and, in time of crisis, students can leave the classroom but the intruder can’t get in. Electric strikes are used as parts of many electronic access control systems to provide added security and conveniences such as traffic control and remote release.

Mechanical Locks: The Basics

Mechanical locks come in four variations—mortise, cylinder, spring bolt, and deadbolt. Let’s look at the pros and cons of each type.

Mortise: A mortise lock requires a pocket—the mortise—to be cut into the door into which the lock is to be fitted. Included are the lock body (the part installed inside the mortise cut-out in the door); the lock trim (which may be selected from any number of designs of doorknobs, levers, handle sets, and pulls); the aforementioned strike plate; and the keyed cylinder which operates the locking/unlocking function of the lock body.

The biggest drawback to a mortise lock is the skill needed to install it. Because the frame of the door must be carved out to accommodate the lock body, familiarity with woodworking and the tools of the trade are a must. However, the mortise lock is stronger than the typical bored cylindrical lock.

Cylinder: A cylinder lock is constructed with a cylinder that a locksmith can easily unscrew to facilitate rekeying. The first advantage to a cylinder lock is that the cylinder may be changed without altering the bolt work hardware. The second is that it is usually possible to obtain cylinders in different formats, providing different levels of security, which can all be used with the same type of key. This lets user have like-keyed and master-keyed systems incorporating a wide variety of different types of locks. Cylinder locks are vulnerable to a technique known as “lock snapping” or “cylinder snapping,” where force is applied to the lock until it breaks into two pieces.

Spring bolt: A spring bolt is a spring-loaded bolt with an angled edge. When the door is pushed closed, the angled edge of the latch bolt allows it to retract. Once the door is fully closed, the spring engages and the latch bolt fully extends and holds the door closed. The latch bolt is retracted typically when the user turns the door handle, which manually retracts the latch bolt, allowing the door to open.

Deadbolt: A deadbolt cannot be moved to the open position except by rotating the lock cylinder. Compared to a spring bolt lock, a deadbolt makes a door more resistant to entry without the correct key. A deadbolt is often used to complement a spring-bolt lock on an entry door to a building.

Mechanical Lock Features

Functions available with mechanical locks include the following:

Classroom Security Lock: This lock is probably the most important lock function for a school. It is also important in other organizations. This lock lets an individual immediately lock a door from inside with a key, eliminating exposure outside the room in a hostile intruder situation. The ability to key-lock from inside the room allows the teacher and/or occupants to stay in or go out in an emergency. As of July 1, 2011, California Law AB 211 Article 8.5 requires all new construction projects submitted to the Division of the State Architect to include locks that allow doors to classrooms and rooms with occupancy of five or more persons to be locked from the inside, except as specified.

Corridor Lock: This lock is locked or unlocked by a key from the outside and a pushbutton or thumb turn from the inside. Users turn the inside lever or close the door to release the button. When outside, the lever is locked by a key and it can only be unlocked by a key. The inside lever is always unlocked.

Entrance/Office Lock: A pushbutton or thumb turn locks the outside lever until it is unlocked with a key or by turning the inside lever. The inside lever is always free for immediate egress.

Vestibule Lock: The latch is retracted by a key from outside when the outside lever is unlocked by key in the inside lever. The inside lever is always free for immediate egress.

Maglocks Defined

An electromagnetic lock, also called a magnetic lock or maglock, consists of an electromagnet and an armature plate. There are two main categories of maglock, the fail safe and fail secure. By attaching the electromagnet to the door frame and the armature plate to the door, a current passing through the electromagnet attracts (fail safe) or releases (fail secure) the armature plate.

A fail safe magnetic lock requires power to remain locked and is not suitable for high security applications, because it is possible to bypass the lock by disrupting the power supply. However, fail safe maglocks are well suited for use on emergency exit doors, because they are less likely to fail to unlock.

Fail secure maglocks use a permanent magnet to keep the door shut and use current passing through an electromagnet to cancel out the permanent magnet and release the door. These fail secure locks are therefore better suited to high security installations. Because power is required to release the fail secure locks, much more care is needed when deciding to use them for safety reasons. For example, if a fire occurs and the power to the building is cut, there might be no means of escape for occupants.

Electronic Lock Basics

Functions available with electronic locks include:

Same as Mechanical: Electronic locks have all the functions of mechanical locks plus two more.

Office: The lockset is normally secure. This lock meets the need for a lockdown function for safety and security. The inside lever is always free for immediate egress.

Privacy: The lockset is normally secure. The interior pushbutton will disable normal electronic access from the exterior. The inside lever is always free for immediate egress.

Types of Electronic Locks

First of all, an electronic lock as described above is controlled by a reader—keypad, card reader, or biometric terminal. If the user has the right personal identification number (PIN), card, or biometric, the door unlocks. Typically readers are installed next to the door. There are also two other types of locking systems.

Standalone Locks/Readers: These combination locks/readers offer a variety of options allowing facility managers to customize the right solution for a specific facility. Keypad only, proximity, magnetic stripe and dual credential plus PIN options are available. On some units, a key-in-lever design also lets users leverage existing master key systems. Management can control where people go and when by setting up access rights and schedules in a central database which gets transferred to the locks using software with a handheld device. With some versions, audit trails can provide visibility as to who accessed a door and when.

Modular All-in-One Locking Systems: These locks combine the lock and reader so that a facility manager can now choose the specific electronic lock needed at the current moment with full confidence that it can be later upgraded without ever taking it off the door. Components that have been traditionally located around the door are now integrated into the lock itself to yield a smarter solution and more value for the investment. The locks provide multiple, interchangeable credential reader modules as well as interchangeable offline, wired, and wireless networking modules so access control can be installed at doors where it was previously unfeasible. The locks are compatible with all popular exit devices, provide a host of power and cylinder options, offer field configurable settings, and include a wide variety of finishes and levers.

Knowing the jargon for locks will help facility professionals convey a feeling of confidence that the best possible security and safety system for the organization has been created.

Dalton-Noblitt is director of vertical marketing at Allegion PLC.