Locksmith Glossary

121 terms from the trade, in plain language. What a wafer is, what a Grade 1 deadbolt actually promises, why a transponder key is not the same as a remote.

121terms

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A B C D E F G H I K L M N P R S T U V W

A

Actuator: The rod or arm inside a car door that the lock cylinder pushes to throw the latch. When a key turns freely but the door stays locked, a broken actuator is usually why. See also Linkage.
ANSI Grade: The American National Standards Institute rating for lock strength, from Grade 3 up to Grade 1. Grade 1 is commercial duty and survives the most cycles and the most force. See also Grade 1.
Anti Drill Pin: A hardened steel insert set in a lock body or cylinder to blunt a drill bit. Standard on most high-security cylinders and on safe locks.
Anti Pick Pin: A driver pin shaped as a spool, mushroom or serrated pin so it catches in the shear line and gives a false set. It makes picking slower and noisier rather than impossible. See also Spool Pin.
Armored Front: A steel plate protecting the face of a mortise lock or a safe lock so the cylinder cannot be pulled or punched out.
Astragal: The strip covering the gap where a pair of doors meet. It blocks a shim or a knife from reaching the latch.

B

Backset: The distance from the edge of the door to the center of the bore hole, almost always 2 and three eighths or 2 and three quarter inches in North America. Ordering the wrong one is the most common reason a new lock will not fit.
Biaxial: A Medeco keying system where each pin is both rotated and elevated, giving far more combinations than a standard pin stack and making a key much harder to copy.
Bible: The upper part of a cylinder holding the driver pins and springs. On a mortise cylinder it can often be opened to rekey without pulling the whole lock.
Bit Key: The old skeleton style key used in warded locks and furniture. Still found on antique interior doors and cabinets.
Bitting: The pattern of cuts along the blade of a key, written as a string of depth numbers. Bitting plus keyway is everything needed to cut a working key. See also Code Cutting.
Blank: An uncut key with the right profile for a given keyway. Cutting starts with the correct blank or nothing else matters. See also Keyway.
Bolt: The moving metal bar a lock throws into the frame. A deadbolt has no spring and cannot be pushed back. A latch bolt is spring loaded and can. See also Deadbolt.
Bolt Throw: How far a deadbolt extends past the door edge. One inch is the usual minimum for a residential deadbolt worth fitting.
Bore Hole: The large round hole through the face of the door that the lock body sits in, usually 2 and one eighth inches across.
Boring Jig: The clamp and guide used to drill the bore hole and the edge hole square and in line. Doing it by eye ruins doors.
Bump Key: A key cut to the deepest depth on every position, tapped so the pins jump the shear line. Modern pin designs and security pins defeat most bumping.
Bypass: Opening a lock by working around its mechanism rather than through it, for example slipping a latch or reaching the thumb turn. Almost always faster and cheaper than drilling. See also Loiding.

C

Cam: The flat tail on the back of a cylinder that turns and moves the bolt or latch. Cam shape and position decide whether a cylinder fits a given lock.
Change Key: The everyday key that opens one lock in a master keyed system. Each door has its own. See also Master Key.
Code Cutting: Cutting a key from its bitting numbers rather than by copying an existing key. It produces a key to factory spec instead of copying wear. See also Bitting.
Combination Lock: A lock opened by a sequence rather than a key, mechanical on a dial safe or electronic on a keypad.
Construction Keying: A temporary key set used while a building is being built, cancelled by turning the real key once for the first time. Saves rekeying the whole site at handover. See also Lost Ball.
Control Key: A key that removes an interchangeable core from its housing rather than operating the lock. Whoever holds it can rekey a whole site in minutes. See also Interchangeable Core.
Core: The removable plug assembly of a lock, holding the pins and the keyway.
Cut Depth: How deep a single cut is made into the key blade, numbered by the manufacturer. Depths run shallow to deep and a one step error can still open or can fail intermittently.
Cycle Test: The lab test that opens and closes a lock hundreds of thousands of times. It is what separates an ANSI Grade 1 from a Grade 3. See also ANSI Grade.
Cylinder: The keyed part of a lock, holding the plug, the pins and the springs. Rim, mortise, key in knob and euro profile are the common shapes.
Cylinder Guard: A hardened ring around a cylinder that stops it being gripped and pulled or snapped.

D

Dead Latching Plunger: The correct name for the small pin beside a latch bolt that blocks it from being pushed in. See also Deadlatch.
Deadbolt: A bolt with no spring that can only be moved by the key or the thumb turn. Single cylinder means a key outside and a thumb turn inside. Double cylinder needs a key on both sides. See also Bolt.
Deadlatch: The small plunger beside the main latch on a good lockset. Held in by the strike, it stops the latch being slipped with a card. See also Loiding.
Decoding: Working out a lock's bitting without a key, by reading the pins, using a decoder tool or reading the code off a factory record.
Dimple Key: A key cut with dimples on the flat faces instead of notches on the edge. Common on high-security European cylinders.
Door Closer: The arm and cylinder that pulls a door shut at a controlled speed. Required on fire doors.
Door Prep: The pattern of holes already cut in a door. Standard prep fits most locks. Non standard prep means filling, cutting or a different lock.
Drilling: Cutting through a lock or safe to open it, the last resort. It destroys the lock and on a safe it has to be done to a known point or the relocker fires. See also Relocker.
Driver Pin: The upper pin in a pin stack, pushed down by the spring. When the right key lifts each stack, the gap between driver and key pin lines up with the shear line. See also Shear Line.
Drop Key: A key left with a neighbor or an agent for access. A weak point in any key control policy.

E

Egress: Getting out. Life safety codes require free egress from the inside of almost any occupied space without a key, a code or special knowledge. See also Panic Hardware.
Electric Strike: A powered strike plate that releases the latch when energized or de energized. It replaces the strike, not the lock.
Emergency Key: The mechanical key hidden inside a smart lock or a car fob for when the battery dies. Most people do not know they have one.
Escutcheon: The plate around a cylinder or handle, decorative on a house and protective on a commercial door.
Euro Profile: The standard cylinder shape across most of Europe and common on patio and storefront doors in North America. Fixed by a single screw through the lock body.

F

Fail Safe: A powered lock that unlocks when power is lost. Used where getting out matters more than staying locked, such as a stairwell door. See also Fail Secure.
Fail Secure: A powered lock that stays locked when power is lost. Used where the asset matters more than convenience, and only where egress is handled another way. See also Fail Safe.
False Set: The feeling when a security pin catches at the shear line and the plug rotates slightly but will not turn. It tells a picker the lock has security pins. See also Spool Pin.
Fire Door: A rated door assembly meant to hold a fire back for a stated time. Fitting the wrong hardware or drilling a new hole voids the rating.
Fire Rating: How long a door, frame or safe is certified to resist fire, stated in minutes or hours. On a safe it is about protecting contents, not about resisting attack. See also UL Rating.
Fob: The remote that locks, unlocks and sometimes starts a car. Separate from the transponder function even when they share a plastic shell. See also Transponder Key.
Follower: The cylinder of plastic or brass pushed in behind a plug so the driver pins and springs stay in the bible while the plug comes out.

G

Grade 1: The heaviest ANSI grade, tested to a million cycles and the highest force. What belongs on a commercial entrance. See also ANSI Grade.
Grand Master Key: A key that opens every lock under several master keys, one level above a master in a keying tree. See also Master Key.

H

Hardplate: A layer of hardened or composite material inside a safe door that stops a drill bit. Good hardplate turns a ten minute drill into an hour.
High-security Cylinder: A cylinder certified to resist picking, drilling and key copying, usually with a patented keyway so blanks are controlled. UL 437 and ANSI 156.30 are the tests that matter.
Hollow Metal: A steel door and frame filled with honeycomb or insulation. Standard on commercial buildings.

I

Immobilizer: The car system that will not let the engine start unless it reads a recognized chip. Fitted to almost every car since the late nineties. See also Transponder Key.
Impressioning: Making a working key by marking a blank in the lock, filing where the pins bite, and repeating until it turns. Slow, quiet and leaves a real key behind.
Interchangeable Core: A core that lifts out with a control key so a lock can be rekeyed in seconds without tools. Small format and large format are the two families. See also Control Key.

K

Key Cabinet: A controlled cabinet holding site keys, signed in and out. The paperwork is what makes a master key system survive staff turnover.
Key Code: The manufacturer's reference for a key's bitting. A direct code gives the cuts outright. An indirect code needs a chart to look up. See also Bitting.
Key Control: The rules and the patent that decide who can cut a copy of a key. Without it a master key gets copied at a hardware counter and the system is gone. See also Restricted Keyway.
Key Fob Programming: Teaching a car to accept a new remote or chip, done through the diagnostic port with the right tool and often a security pin from the maker.
Key Gauge: A small steel card used to read cut depths off a key by eye. Quicker than a micrometer and accurate enough to cut from.
Key Machine: The cutting machine that duplicates or code cuts keys. A duplicator traces an existing key. A code machine cuts from numbers. See also Code Cutting.
Key Pin: The lower pin in a stack, the one the key actually touches. Its length is what the cut depth is chosen for. See also Driver Pin.
Keyed Alike: Several locks set to open on one key. What most people want when they move into a house with four different keys.
Keyed Different: Locks that each take their own key and share nothing.
Keyless Entry: Any system that opens without a metal key, from a keypad deadbolt to a car that unlocks as you walk up to it.
Keyway: The shaped slot a key slides into, and the profile that decides which blanks fit. Restricted keyways are the basis of key control. See also Blank.

L

Laser Cut Key: A car key milled with a track along the middle of the blade rather than notches on the edge. Also called a sidewinder or internal cut key. See also Sidewinder.
Latch: The spring loaded bolt with an angled face that lets a door close without turning anything.
Linkage: The rods connecting a car door handle and lock cylinder to the latch. Reaching it through the window gap is a common bypass on older cars. See also Actuator.
Lishi: A brand of pick and decoder made for one specific keyway, which picks and reads the cuts at the same time. It turned car opening from a craft into a repeatable job.
Loiding: Slipping a latch with a card or a shim. A deadlatch defeats it, a plain spring latch does not. See also Deadlatch.
Lost Ball: A construction keying method using an extra ball bearing in the pin stack that drops out of reach on first use of the permanent key.

M

Maison Keying: A scheme where one key, usually the tenant's, also opens shared doors such as a lobby or a laundry room.
Master Key: A key that opens every lock in a group, each of which also has its own change key. Built by adding a master wafer to each pin stack. See also Master Wafer.
Master Wafer: The thin extra pin that creates a second shear line in a stack so two different keys will turn the plug. Also called a spacer. See also Master Key.
Mortise Cylinder: A threaded cylinder that screws into a mortise lock body, driving the lock through a cam. See also Cam.
Mortise Lock: A lock body set into a pocket cut in the edge of the door. Heavier, more serviceable and far more common on commercial doors than on houses.
Mule Key: A blank or cut key used to turn a lock while the real key is being made, or to test a plug during service.

N

Night Latch: A rim lock fitted to the inside face of the door, often with a snib to hold the latch back or deadlock it.

P

Padlock Shackle: The U shaped bar of a padlock. A shrouded shackle sits inside the body so bolt cutters cannot reach it.
Panic Hardware: A push bar that unlocks a door with one motion in the direction of travel. Required on many exits regardless of what the lock does from outside. See also Egress.
Pick Gun: A tool that snaps all the pins upward at once so they jump the shear line. Fast on cheap locks, poor on security pins.
Pin Stack: One column inside a cylinder, made of a spring, a driver pin, any master wafers and a key pin. A five pin lock has five of them.
Pin Tumbler: The lock design almost every key in North America opens. Spring loaded pin stacks block the plug until the right key raises each one to the shear line. See also Shear Line.
Plug: The rotating part of a cylinder holding the keyway and the key pins. It turns only when every stack is at the shear line.
Plug Spinner: A tool that flips a plug quickly the other way when a lock has been picked in the wrong direction, saving a repick.
Push Button Lock: A mechanical keypad lock with no battery and no wiring. Common on staff doors and gates.

R

Rekey: Changing which key operates a lock by swapping the key pins, leaving the same hardware on the door. Faster and cheaper than replacing the lock. See also Key Pin.
Relocker: A hidden bolt inside a safe door that fires if the lock is punched or the door is drilled in the wrong place. It locks the safe permanently until a professional opens it. See also Drilling.
Restricted Keyway: A keyway whose blanks are patented and sold only to authorized dealers, so a copy needs proof of authority. The practical basis of key control. See also Key Control.
Rim Cylinder: A round cylinder with a tail piece, fitted through the door to a lock mounted on the inside face.
Rolling Code: A remote or fob that sends a different code every press, so a recorded signal cannot be replayed. Standard on cars since the late nineties.

S

Sargent and Greenleaf: A maker of safe locks, mechanical and electronic, whose dial locks are a common sight on gun safes and commercial units.
Schlage: A major American lock maker. Its C keyway is one of the two profiles most residential keys in the country are cut on.
Scope: A borescope used to look inside a lock or through a drill hole in a safe, so the opening is made to a target rather than by guessing.
Shear Line: The gap between plug and housing. When every pin stack is split exactly at it, the plug turns. Everything a pin tumbler lock does comes back to this line. See also Pin Tumbler.
Shim: A thin strip slid into a lock to hold pins above the shear line one at a time, or into a padlock shackle to release it.
Sidewinder: Another name for a laser cut car key, from the winding track milled along the face of the blade. See also Laser Cut Key.
Slim Jim: A flat steel strip once used to reach car door linkage through the window channel. On modern cars it damages wiring and airbag sensors, and the trade has largely left it behind. See also Linkage.
Snap Attack: Snapping a euro cylinder at its center screw hole and pulling the halves out. Anti snap cylinders are cut to break in a harmless place instead. See also Euro Profile.
Snib: The small catch on a night latch that holds the latch open or deadlocks it.
Spool Pin: A driver pin waisted in the middle so it catches and gives a false set under tension. The most common security pin. See also False Set.
Strike Box: The metal pocket behind a strike plate that stops the bolt tearing through the frame.
Strike Plate: The metal plate on the frame the bolt goes into. Three inch screws into the stud through the strike do more for a door than a better lock does.

T

Tailpiece: The flat bar on the back of a rim or knob cylinder that drives the lock. Cut to length for the door thickness.
TDD: Total door drop, the trade shorthand for a door assembly that has failed at the frame rather than at the lock.
Tension Wrench: The L shaped or Z shaped tool that applies light rotation to a plug while the pins are picked. Also called a turning tool, and it does most of the work.
Thumb Turn: The small lever on the inside of a deadbolt that throws the bolt without a key. It is also what a bypass tool reaches for.
Transponder Key: A car key with a chip in the head that answers a challenge from the immobilizer. Cutting it is only half the job, the chip has to be programmed too. See also Immobilizer.
Tubular Lock: A lock with pins arranged in a circle around a round key, common on vending machines, bike locks and some cabinets.

U

UL 437: The Underwriters Laboratories test for high-security cylinders, covering picking, drilling and forcing for a stated number of minutes.
UL Rating: The Underwriters Laboratories class for a safe, such as TL 15 or TL 30, meaning it resisted tool attack for that many minutes by a trained technician with known tools. See also Fire Rating.

V

VATS: General Motors Vehicle Anti Theft System, an early resistor chip in the key blade. Predates transponders and still shows up on nineties cars.

W

Wafer Lock: A lock using flat spring loaded wafers instead of pin stacks. Common on cabinets, desks and older car doors, and much easier to pick than a pin tumbler.
Wafer Pack: The set of wafers in a car door or ignition lock, read and rebuilt when a lock is serviced rather than replaced.
Wafer Thickness: The size step between wafer positions in a wafer lock, the equivalent of cut depth in a pin tumbler.
Warded Lock: An old design where fixed obstructions block the wrong key shape. Almost no security, still found on antique furniture and padlocks.

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