Terminology By: MMDeveloper;
Last Updated: 2017/07/24

Binding Order
The binding order is the order in which the pins bind up in the lock. It will differ between locks, and if you change the pins, the binding order will generally change with it. Some locks will bind front to back, some back to front, and some random.
Binding Pin
Locks are not perfect, not all pins will bind at the same time; they will typically bind one at a time. A bining pin is a pin that, when the lock is under tension, will be more difficult to push upward than the other pins. This is because it's being squished in the shear line between the plug and the upper chamber.
SPP
Short for "Single Pin Picking", this is a method of lock picking that generally involves a hook to manipulate the key pins, one at a time. It is a more methodical way to pick locks. It also works on all locks. as opposed to other methods, such as raking.
TOK
Short for "Top Of Keyway", this is a tensioning method in which a specially made tension wrench is placed in the top of the keyway (infront of the first pin). This leaves more keyway exposed for other tools.
BOK
Short for "Bottom Of Keyway", this is a tensioning method in which a tension wrench is placed in the bottom of the keyway. This takes up a lot of space but is generalled preferred for raking.
Key Pin
The keypin is the pin that physically touches the key in the lock
Driver Pin
The driver pin(s) are the pins that sit on top of the key pin. They are what provide the shear lines in the pin stack.
Pin-in-Pin
This is common with Mul-T-Lock and their imitators. This is when there is literally a pin within a pin. The outer pin will have a hole drilled through the center in which a smaller inner pin will live. It doubles the number of pins needing to be picked to shear, and also adds more shear lines needing to be dealt with.
Shear line
The shear line is where two separate parts meet. One shear line is between the key pin and driver pin (or driver pin and additional driver pins in the event of a lock that's on a masterkey system. The other shear line is between the plug and the core. The pins will be inbetween the shear line of the plug/core and the philosophy of picking a lock is making the plug shearline match up with the pin shear line.
Plug
The plug is the rotating part of a lock that accepts your key.
Lock Core
The core of a lock is the part of the lock in which the plug lives. The plug and plug body assembly are generally referred to as the "core".
Lock Body
The lock body is the housing that holds the lock core. Generally this is referring to deadbolts, mortise cylinders, and the like.
KIK
Short for "Key In Knob". This is the most common lock core that's found in padlocks, door knobs, and some other locks. The profile of a KiK looks like
Bible
In reference to the KIK, the Bible is the thin piece that's on top of the plug. This is where the driver pins and main springs live.
Main Spring
This is the spring that is above the top most driver pin. This provides all of the spring tension for its chamber.
Warding
The warding of a keyway refers to the little shelves and protrusions in the design of the keyway. It provides the shape and sometimes some pick resistance.
Tailpiece
The tailpiece is the part(s) attached to the rear of the plug. This generally is what allows the lock core to interact with the lock body and its locking mechanisms.
Countermilling
Countermilling is a term used to define modifications to a pin chamber that would cause a pin to hang up on it. Generally if the chamber is slightly more narrow than the top opening of the chamber, leaving a distinct ledge at the top. Countermilling can also appear on a driver pin. This generally looks like a very sharply cut spool.
Bitting
Bitting refers to the profile of the teeth cut in the key. This corresponds to the length of the key pins in the lock. Each cut has a depth and different lock brands have different cut depths and different keys offer a different number of cuts.
Operating
Operating is typically referring to the normal unlocking of a lock.
Control
Control refers to Interchangeable Cores (I.C.) and their ability to be removed from the lock body. Putting a lock into the Control position usually requires a special key.
SFIC
Short for "Small Format Interchangeable Core", most commonly the "Best" brand locks. This is a standardized removable core.
LFIC
Short for "Large Format Interchangeable Core", most commonly used with Medeco brand I.C. cores. LFIC is not a standard and are usually proprietary to the manufacturer.
Masterkey
This refers to a lock that can be opened by more than one key. This is common with businesses in which one key can open many doors (such as for housekeeping) and those same doors can be opened by a different key that can't open the same group of doors. Think of hotels in which each room has a lock. You are given a key to your room that will only open your door. Maintenance however has a key that will open all the doors.
Construction Keying
This is similar to Masterkeying except one key will open a lock until a different key is used in the lock. Once this second key is used, the first key will no longer operate the lock. This is helpful if you need to give a contractor access to your house while you're at work. The contractor can gain access through your door until you get home and open the lock with your key. The moment you use your key, the contractors key will no longer work in your lock.