Quick Guide: The Basics of Keying
In the door industry, the term “keying” refers to the way keys will be used to operate the cylinders that are installed in the door hardware throughout the building or space. Keys can be assigned to certain groups that define where they will and will not operate the cylinders. Keying determines which keys work at each opening. Here we will discuss the way a cylinder can be set up to allow for certain types of keying.
A cylinder will contain a certain number of pin chambers generally ranging from 5 pin chambers up to 7. The pins vary in height and this variation in height is what gives the cylinder its “combination”. When a key with the matching combination is inserted, the pins move up and create what is called a “shear line”. This shear line allows the cylinder to rotate thereby operating the cylinder which then locks or unlocks the hardware. (Learn more about cylinders in this previous blog post: How To Unlock The Mystery of Cylinders)
Types of Keying
Cylinders are keyed using pins a certain way and then keys are cut to operate that cylinder.
Keyed Different (KD)
When cylinders are all keyed different it means that each lock is operated by a unique key. Every cylinder will have its own unique combination and therefore will only be operated by its own unique key. A key used at one door cannot be used to open any other doors. An example for where this might be used is in an office space where no one needs access to any of the other office doors except their own.
Keyed Alike (KA)
When cylinders are all keyed alike it means that every lock is operated by the same key. A single combination will be used at every cylinder meaning one key will operate every cylinder. This is useful in a space where a limited number of keys is required, such as areas with storage closets or common rooms that only need one combination.
Master Keyed (MK)
Cylinders that have been master keyed have one or more master pins on top of the standard pins. Master pins will create an additional shear line that allows the master key that matches the master pin combination to operate the cylinder. The master pin combination can be used in cylinders where someone with higher clearance needs to have access, such as the building owner or the company president. Any cylinder that has been master keyed will operate with the master key as well as the standard operating change key.
Single Keyed Different (SKD)
Sometimes a cylinder should be not be operated by a master key or even a grand master key and only operated by its own key. Perhaps there is sensitive or highly protected material that needs to be secure. By having a cylinder single keyed different only one key combination can be used at that opening.
The less keys that operate a cylinder the more secure it will be.
A cylinder that has been cross-keyed means it can be operated by more than one change key. This is different than a master keyed cylinder because usually a cylinder that is master keyed will only be operated by one change key as well as the master key. A cross keyed cylinder allows multiple change keys to operate it.
For example, a set of offices may be located behind a hallway door that is locked. You may want each office occupant to have access to the hallway door but not each other’s office doors. So the hallway door cylinder will be cross-keyed to allow each person’s key to operate the hallway door and their own office door.
Caution is advised when specifying cross-keying. This is because each additional combination will require additional pins in the cylinder chambers. Each level of pins creates a new “shear line” which allows keys to rotate and operate the cylinder. Each additional shear line creates the possibility of what are called “ghost keys”. These are keys that will operate the cylinder even though those keys are not supposed to operate that cylinder. More shear lines also makes it easier for that lock to be picked.
As technology advances and evolves, electronic access control has become a robust solution for many scenarios that are mentioned above. Access control is accomplished using keypads, key cards, and other types of credentials.
The benefits of access control include the ability to add and remove credentials using computer software instead of making changes to the physical door hardware (such as removing and replacing keyed cylinders or physically cutting new keys). Access control can also help keep track of who has accessed certain openings and when they opened them. Schedules can also be set up on the system to only allow access during certain times of the day. Temporary access can also be granted if necessary.
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