What Is Inside a Standard Door Lock?
Most home and office locks in the Valley are pin-tumbler locks, and a good share of this glossary names some part of one. The whole idea fits in one drawing: the right key lifts every stack of pins to exactly the right height, the splits line up on the shear line, and the plug is free to turn.
Everything else follows from that picture. Rekeying swaps the key pins so a different key lines them up. A master pin adds a second split so two keys can do it. Bumping and picking try to get the same alignment without the key, which is exactly what security pins are there to make harder.
What Is Inside a Modern Car Key?
A newer car key is often three things in one housing: a metal blade that turns a lock, a transponder chip the immobilizer checks before the engine will run, and a remote or proximity fob. Cutting handles the blade; programming handles the other two. That split is why a car key costs more than a house key.
The honest do-it-yourself part: when a fob quits, try a fresh coin battery before anything else, and learn where your emergency key and its keyhole are before the day you need them. In Arizona, heat is the fob's main enemy; our guide on why fobs fail in the heat covers what to do about it.
Locksmith Terms, A to Z
Each entry gives the short version first. The links marked More go to the guide or service page that explains the topic properly, so you can stop at the definition or keep reading.
A
- Access control
An electronic way to decide who can open a door — keypad codes, key fobs, cards or a phone app — instead of, or alongside, metal keys. The practical win is that you delete one person's code or credential instead of rekeying the door when they leave.
- All keys lost (AKL)
The car-key job when no working key exists. The locksmith decodes the lock or gets the key code, cuts a new blade and programs the new key to the immobilizer, on many makes erasing the lost keys at the same time. Ours starts from $349, and the tech confirms the exact price on-site before work begins.
More: Lost all your car keys?
- ANSI/BHMA grade
The Grade 1, 2 or 3 rating on a lock's box, from lab testing for durability and resistance to force under standards written by the Builders Hardware Manufacturers Association (BHMA) and approved by ANSI. Grade 1 is the strongest, Grade 2 is the sensible standard for most homes, and Grade 3 is builder-basic.
- Anti-lift screws
Screws set in the upper track of a sliding glass door and backed out until their heads sit just above the moving panel. They stop the panel from being lifted out of its track, which the factory latch does nothing about.
More: Sliding glass door locks
B
- Backset
The distance from the edge of the door to the center of the bore hole where a knob or deadbolt mounts. Most residential locks are made for 2-3/8 or 2-3/4 inches, and many latches adjust to either; the lock has to match the door.
More: Smart lock installation
- Bitting
The pattern of cuts along a key blade — how deep each cut is at each position. It's usually written as a string of numbers, one per cut, and rekeying a lock means setting its pins to match a new bitting.
More: Rekey vs. replace a lock
- Blade (key blade)
The metal part of a key that goes into the lock. House keys and older car keys have cuts along the edge; many modern car keys are laser-cut, with a groove milled along the flat side instead.
- Bore hole
The large round hole through the face of a door where a knob, lever or deadbolt mounts. Most residential locks fit a standard 2-1/8-inch bore; older or unusual doors sometimes need adjustment.
- Bump key
A key cut to the deepest depth at every position, used to jolt the pins of a pin-tumbler lock so the plug can turn for an instant without the right key. Security pins in better cylinders are built to resist it.
C
- Change key
In a master key system, the everyday key that opens only its own door or group of doors. A staff member's change key opens their office; the master key above it opens everything in the group.
- Cylinder
The part of a lock the key goes into: a housing with the plug, pins and springs inside. It can often be rekeyed or swapped without replacing the rest of the lock.
More: Rekey vs. replace a lock
D
- Deadbolt
A lock with a square-ended bolt that moves only when a key or thumbturn turns it, so it can't be pushed back like a spring latch. A good one throws its full inch into a strike plate anchored in the door frame.
- Deadlatch
A spring latch with a small extra plunger beside the angled bolt. When the door is closed the plunger is held in, and it blocks the latch from being pushed back with a card or shim.
- Dealer-only (car keys)
A vehicle whose key registration needs the manufacturer's own dealer system, so aftermarket programming equipment can't add a key. Late-model European cars — BMW, Mercedes, Audi — often fall here, as do some brand-new models; we tell you on the phone, for free.
- Decoder (Lishi 2-in-1)
A precision hand tool that reads the depth of each wafer or pin inside a lock, giving the key code without taking the lock apart. The Lishi 2-in-1 is a common example: one tool both opens a specific lock type and decodes it, which is how a car key can be cut when no key exists.
- Double-cylinder deadbolt
A deadbolt that needs a key on both sides, with no thumbturn inside. People choose it for doors with glass in or beside them, but nobody can get out that door in an emergency without the key, so check local code before putting one on an exit door.
E
- Emergency key
The mechanical blade hidden inside most smart keys and many remote fobs, released by a small button or slide. It opens the driver's door when the fob battery is dead; on some cars the door keyhole hides under a cap on the handle.
More: Key fob stopped working?
- Exit device (panic bar)
The horizontal push bar on a commercial exit door. One push from inside opens the door while it stays locked from outside, and on many commercial doors it's a code requirement rather than an option.
More: Master keys, rekeys & staff turnover · Commercial locksmith services
G
- Grand master key
The top key in a larger master key system: one key that opens every lock across several buildings or suites, while each site's master key still opens only its own site.
H
- High-security lock
A lock built to resist picking, bumping and drilling well beyond an ordinary lock, typically with security pins, hardened inserts and a key that can't be copied without authorization. No lock is unopenable; high-security hardware raises the time, skill and noise it takes.
I
- Ignition cylinder
The keyed lock you turn to start a car that uses a traditional key. Over the years the wafers inside and the key itself wear, which is one common reason a key sticks or won't turn.
- Immobilizer
The anti-theft system in a car's computer that lets the engine run only when it recognizes a registered transponder chip or smart key. It's why a copied metal key can turn the ignition and still not start the car.
More: Car key programming
J
- Jamb
The vertical part of the door frame that the door closes against, where the strike plate is mounted. On most homes the jamb board is what splits when a door is kicked, which is why 3-inch screws into the stud behind it matter.
K
- Key code
A short code that stands for a key's bitting, so a key can be cut by machine without the original in hand. For cars, the code can sometimes be looked up by VIN or read from the lock with a decoder.
More: Lost all your car keys?
- Key fob
The handheld remote that locks, unlocks and opens the trunk, powered by a small coin battery. It can be a separate fob or built into the key head, and a fob that suddenly quits usually needs a new battery before anything else.
More: Key fob stopped working?
- Keyed alike
Several locks set up to open with the same key, like the front, back and garage-entry doors of one house. It works when the locks share a keyway, which usually means the same brand.
- Keyway
The shaped slot in a cylinder that the key slides into, matched by the profile milled along the key blade. Brands use different keyways — a Kwikset key won't even enter a Schlage lock — which is why mixed brands can't always share one key.
- Knob lock
A doorknob with a lock built in, holding the door with a spring latch rather than a bolt. Fine on interior doors; on an exterior door it should be paired with a deadbolt.
L
- Laser-cut key (sidewinder)
A car key with a wavy groove milled into the flat side of the blade instead of cuts along the edge. It's cut on a computer-controlled machine from a key code or an existing key, not on a basic duplicator.
- Lever handle
A door handle you press down instead of turn, easier with full hands or limited grip. Entry levers lock with a spring latch just as a knob does, so an exterior door still needs a deadbolt.
- Lockout
Being shut out of your car, home or business with no working key on hand. Ours are flat-rate: from 7AM to 8PM a car lockout is $139, a home lockout $159 and a commercial lockout $199, with a flat +$60 after 8PM.
M
- Master key system
A hierarchy of keys in which each lock answers to two keys: its own change key and a master key above it. Everyone carries one key that opens exactly what their job needs, and when someone leaves you rekey only the doors their key opened.
- Master pin
A small extra pin added to a pin stack so the stack can split at the shear line in two places — one for the change key, one for the master key. It's how master keying works, and why a poorly planned system can let keys nobody intended open a door.
- Mortise lock
A lock whose mechanism sits in a rectangular box fitted into a deep pocket (the mortise) cut into the edge of the door, with the cylinder screwed into the box. Common on commercial doors and some older or high-end homes.
N
- Non-destructive entry
Opening a lock without damaging it — picking, bypass tools or decoding — so it still works afterward. When a lock can't be opened that way in reasonable time, drilling the cylinder core is the standard fallback, and it should be explained and agreed before it starts.
O
- OBD-II port
The diagnostic socket under the dashboard that shops use to talk to a car's computers. Key programming runs through it, the same channel the dealer uses, to register a new key with the immobilizer.
P
- Pin tumbler
The most common lock mechanism in homes and offices. Springs push stacks of driver pins and key pins across the gap between plug and housing, blocking the plug; the right key lifts each stack so its split sits exactly on the shear line, and the plug turns.
More: The pin-tumbler diagram above · Rekey vs. replace a lock
- Plug
The inner part of a cylinder that turns when the right key is in; the keyway runs through it. Rekeying means taking the plug out and swapping its key pins.
More: Rekey vs. replace a lock
- Programming (car key)
Registering a new key's transponder chip, and its remote or smart functions, with the car's computers using diagnostic equipment, usually through the OBD-II port. It's a separate step from cutting the blade, and we program the keys and fobs we supply ourselves.
More: Car key programming
- Push-to-start
A car that starts with a button instead of a turned key, as long as the smart key is inside. If the fob battery dies, most still start when you hold the fob against the start button or set it in a marked spot — your owner's manual shows where.
More: Key fob stopped working?
R
- Rekeying
Changing the pins inside your existing lock so old keys stop working and a new key does, while the hardware stays on the door. Ours is $149 for the first door and +$49 for each additional door, so a typical 3-door home is $247.
More: Rekey vs. replace a lock
- Relocker
A backup locking device inside many safes that fires if the lock is attacked — drilled, punched or forced — and holds the bolts shut on its own. Once it has fired, the right combination may no longer open the safe, and opening it becomes specialist work.
More: Safe won't open
- Remote head key
A car key with the transponder chip and the remote buttons built into its head, so blade and remote are one piece; a flip key is the folding version. Both the chip and the remote need programming.
- Restricted keyway
A key profile whose blanks aren't sold openly, so a hardware-store kiosk can't copy the key. Duplicates come only through an authorized source, for people on the owner's signed list.
- Rim cylinder
A cylinder that passes through the door and works a lock mounted on the inside surface — a rim lock, a night latch or many panic bars — through a flat bar on its back. Common on commercial doors and older homes.
- Rolling code
The security method car remotes and smart keys use: each button press sends a new code from a sequence the car and fob share, so a recorded signal can't simply be replayed. It's also one reason a fob can occasionally lose sync with the car.
More: Key fob stopped working?
S
- Security pins
Specially shaped pins, such as spool or serrated pins, that catch and bind when someone tries to pick or bump a cylinder. They add time, skill and noise; they don't make a lock unopenable.
- Service call
A fee that covers a technician's trip to your location. Ours applies to car-key jobs: a $59 service call brings the tech and equipment out to lock the exact price, and it's credited to the job if you go ahead.
More: Full price list
- Shear line
The thin gap between the plug and the housing of a cylinder. When every pin stack is split exactly at that line, nothing blocks the plug and it turns.
- Smart key (proximity key)
A fob the car senses nearby, so you can unlock by touching the handle and start with a button while it stays in your pocket. It talks to the car with encrypted rolling codes, which is why it costs more to replace and has to be paired with professional equipment.
- Smart lock
An electronic lock, usually a deadbolt with a small motor, that opens by keypad code, phone app or fob, often with a backup keyway. It's as strong as the deadbolt it's built on; the electronics change how you get in, not how the bolt resists force.
- SmartKey (Kwikset)
Kwikset's user-rekeyable cylinder, sold as SmartKey Security. With the key that currently works and the small SmartKey tool, you can reset the lock to a new key yourself, following Kwikset's instructions. Not to be confused with a car's smart key.
- Spare key
A second working key, made while you still have one. For a car it's the least expensive time to get one, because adding a key alongside a working key is a smaller job than making one from nothing.
More: Bought a used car with only one key · Where to hide a spare key
- Spring latch
The angled, spring-loaded bolt in a knob or lever that snaps into the strike when the door closes. It holds the door shut but can be pushed back, which is why exterior doors also need a deadbolt.
- Strike plate
The metal plate on the door frame that a latch or bolt goes into. On many homes it's held by short screws in a soft jamb, and a reinforced strike with 3-inch screws into the stud does more against a kick than a pricier lock.
T
- Thumbturn
The small knob on the inside of a single-cylinder deadbolt that throws the bolt without a key, so anyone inside can leave quickly.
- Transponder chip
A tiny chip in the head of a car key or inside a fob that answers the immobilizer when you start the car. It needs no battery, and it has to be programmed to your car before the engine will run.
V
- Valet key
A limited car key, on vehicles that come with one, that opens the doors and starts the car but won't open the trunk or a locked glove box. If it's the only key you got with a used car, it still starts the car, so adding a full key is usually a spare-key job rather than all keys lost.
- VIN
The 17-character Vehicle Identification Number, visible at the lower left of the windshield and printed on your registration card. Locksmiths use it to identify exactly which key your car needs and, on some makes, to look up the key code.
More: Car key programming
W
- Wafer lock
A lock that uses flat, spring-loaded wafers instead of pin stacks. Most car door locks and ignitions use wafers, as do many cabinets and mailboxes, and a decoder reads the wafer depths to recover a key code.
Code questions aren't glossary questions. Where a term touches building or fire code, such as double-cylinder deadbolts and exit devices, the rules vary by city and by type of building. Check with your local building department, landlord or property manager. Nothing on this page is legal advice.
Heard a Word That Isn't Here?
Ask. Any good locksmith will explain a term before work starts: what it means, why it applies to your lock or your car, and what it changes about the price. If a word you heard on a call doesn't match what's on this page, text it to us at (623) 200-4499 and we'll explain it.
Plenty of what's defined here you can handle yourself. A new fob battery, a Kwikset SmartKey rekey when you still have a working key, anti-lift screws in a patio slider, and 3-inch screws in a strike plate are all reasonable weekend jobs. The definitions point to the guides that show how, and say plainly when a job needs equipment you don't have.