Understanding the 20+ Lock FunctionsAuthor: Brian Rhodes, Published on Aug 26, 2013
Some suppose all locks are the same but standards existing defining a range of over 20 different lock functions. Understanding them is vital in ensuring the right unit is specified for a job, or else security vulnerabilities or dangers to life/safety can result. In this note we look at lock functions, the ANSI/BHMA Function codes, which types are most common, and the right functions to use when controlling access.
The 'function' or mechanical behavior of a lock, especially a mortise or cylindrical lever lock, should be specified for an opening. An easy example of different functions in everyday use can be seen when comparing 'restroom/bathroom/WC' locks and 'closet' locks.
Most bathroom locks include the provision to lock from the inside, preserving the privacy of occupants. However, this same feature is not common on closet doors, simply due to the potential of accidentally locking the door shut and preventing access from the outside.
These properties of locks are identified by codes, and there are over 20 different functions available. Codes are segregated according to lock type, meaning the a mortise and cylinder lock with the same function are coded differently. This simplifies specification writing and ordering, condensing complex interactions to a code.
Before codes were implemented, functions were defined via common labels like 'Passage Functions, or 'Privacy Locks'. However regional and manufacturer variations of those labels are common, and simply identifying these locks by common labels does not guarantee the exact function will be ordered. Because many of the 'old guard' still identifies locksets using these terms, they persist.
For accurate and precise descriptions, however, the ANSI/BHMA Function codes should be used:
These are 3 of the most common lock functions specified:
- Office Doors: Most office workers want to lock their doors after hours. The F82/F04 function lets an employee push a button on the back of the lock when they leave, pull the door shut to lock it, and ensure it can only be unlocked by key when unattended.
- Server Rooms: For higher security applications, the addition of a deadbolt is useful. The F88/F09 "Entrance" function allows for an additional deadbolt to be thrown by keyed locking from the outside of the door, when IT leaves a MDF/IDF. However, when personnel is inside the room, the lever functions like a "Privacy" lock allowing free egress.
- Break Room: The F75/F01 "Passage" function is ideal for areas using doors for environmental isolations (noise/HVAC) but do not necessarily want them lockable. Areas like Break Rooms are common access, and "Passage" locks assure they aren't inadvertently or maliciously locked from use.
Other applications certainly exist. For example, for a medical storage closet, F86 is a likely choice because the door is locked all the time and can only be opened by a key. The door automatically locks when the door is shut, which is ideal for securing a closet filled with valuable items. Code F86 also specifies a cylindrical lockset, although if the door was prepped for a mortise lockset, code F07 would provide the same features.
Also, look at Code F84/F05. This function is informally called 'Classroom Function', as they are designed to be installed in schools. These locks always allow occupants out of a classroom regardless if the door is locked or not. However, in order to lock the door, a key must be used on the outside of the room. This orientation has caused some concern in the wake of school shootings, because they potentially expose the teacher or class to danger in order to lock the door. This explains why some products marketed as 'classroom locks' do not specify F84/F05 code compliance, because they can be locked inside the class. While this potentially may be a safer function, it does not meet the formal 'Classroom Function' definition and it is not used.
Most commercial-grade hardware makes finding lock function easy - generally this is listed on cutsheets, and different product SKUs have different functions, even if the base hardware series is the same. Take this example from Yale:
Finding the right function is straightforward and many distributors will ask you for this information if you do not include it. Getting the right function ordered is important, because it is difficult or impossible to change this attribute in the field.
Most residential and light-grade commercial hardware does not specify any function code, and is simply sold as an 'office lock' or 'bathroom lock'. These products are configured in only the most common functions and may not be compliant with codes or specifications as a result.
Simply ordering a lockset because 'it uses a key' and fits within a door is not proper and may be illegal. Certain occupancies outlaw some functions - E2141/F16 "Double Keyed Deadbolt" cannot be used in most group occupancies, while others strictly define required use of others - F93/F15 only on Hotel/Motel doors.
Electronic Access Relevance
Failing to understand lock functions complicate electrified lock hardware selection. For example, if a lock includes a separate deadbolt, an accompanying electric strike may need to upsized to include more that one latch, or more than one strike may be required. Likewise, if a deadbolt is improperly included in a lock in an egress pathway, it could potentially kill or injure people trying to escape.
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