Glossary – Antique Padlocks

A

Actuator: The internal component that transfers the rotational motion of the key plug to the locking bolt or dogs that secure the shackle. In modular mechanisms the actuator is separate from the tumblers; in integrated designs the tumblers act directly on the shackle.
Ancient Lock: A padlock of antiquity — broadly, any lock produced during or stylistically consistent with the Roman, Egyptian, Chinese, or early Medieval periods. On this site, the Ancient Locks category encompasses ball, cloverleaf, heart, cylinder, and ward-box designs from the pre-industrial era. The Latin term is sera pensilis (hanging bolt).
Anti-Pick Pins: Secondary security pins — spool, serrated, or mushroom-shaped — installed in pin tumbler cylinders to resist manipulation. When a pick tool applies false rotational pressure, anti-pick pins create a false set that prevents the plug from turning.
Arched Shackle: The classic U-shaped shackle, bent in an arc over the body of the padlock. The standard form on the majority of antique padlocks.

B

Ball Lock: An ancient padlock type in which the body is spherical or hemispherical. Common in Roman and early medieval Europe; examples typically have an iron body with a bronze or iron arched shackle. Sometimes called a ball and half-ball padlock. — See also: Ancient Lock
Barrel Key: A hollow tubular key used to operate certain lever and warded locks. The key fits over a post in the keyway, and the bit projects from the side of the barrel. Common on older furniture locks; found on some antique padlocks, particularly postal and smokehouse types.
Bit: The projecting blade or wing of a key that engages the tumblers or wards of the lock mechanism. The shape and cut of the bit determines which lock the key can open. Also: the number of bits on a switch key (single-bit, double-bit) describes the key's profile.
Body: The main housing of a padlock — the lower section that contains the locking mechanism, cylinder, and shackle locking points. Bodies may be cast (solid block of metal), stamped (sheet metal pressed into shape), extruded, or laminated. Body material and construction method are primary dating and identification factors.
Bolt: The sliding or rotating bar inside the lock that physically secures the shackle heel or toe in the locked position. When the correct key is used, the bolt retracts to release the shackle. Distinguished from the shackle itself, which is the external loop.
Bow: The ring or loop at the head of a key, used as a grip for turning. On antique padlock keys the bow shape can be diagnostic — round, oval, heart-shaped, coffin, or decorative bows were common on specific lock types or eras.
Bow Shape (Switch Key): On railroad switch keys, the shape of the bow (the looped head of the key) is an important identification characteristic. Common shapes include round, oval, heart, coffin, and oblong. Different railroads and manufacturers favored specific bow shapes.

C

Cartridge: An assembly of tumblers and springs pre-assembled as a unit that can be slid into a lock body. Popularized by Yale & Towne's 1877 lever padlock patent, the cartridge design allowed locks to be rekeyable and simplified manufacturing. The pin tumbler cartridge became standard in 20th-century padlocks.
Case Hardened: A heat-treatment process applied to the outer surface of a shackle or body, creating a harder outer layer while the interior remains tough. Case hardening significantly increases resistance to bolt cutters and hacksaws. Commonly noted as a feature on railroad and high-security padlocks.
Cast Body: A padlock body formed by pouring molten metal into a mold. Cast brass and cast iron bodies were the standard for quality antique padlocks before stamping became economical in the 1870s–1880s. Cast bodies are heavier, more durable, and generally more collectible than their stamped counterparts.
Cloverleaf Padlock: An ancient lock type with a distinctive three-lobed or four-lobed (quatrefoil) decorative body. Found in Roman and early medieval contexts; the cloverleaf shape has symbolic and aesthetic significance. A sub-category of Ancient Locks in this archive.
Coin Padlock: A padlock incorporating an actual coin — typically silver or copper — into the body as a decorative or commemorative element. The coin may form the face, be inset into the body, or the body may be fashioned from the coin itself. Popular among 19th and early 20th century collectors.
Combination Lock: A padlock opened by entering a specific numeric sequence via rotating dials, sliding discs, or push buttons rather than a key. Antique combination padlocks include dial types, button types, clock-face types, and slide-bar configurations. Keyless by design.
Commemorative Padlock: A padlock produced to mark a specific event, anniversary, organization, or occasion — rather than for functional security use. Commemoratives may bear inscribed dates, seals, insignia, or custom markings. A significant collecting category.
Cut-A-Way: A padlock with a section of the body deliberately removed or made transparent (usually a window of clear material) to expose the internal mechanism. Cut-aways were used as teaching and demonstration tools by locksmith schools and manufacturers. Highly collectible.
Cylinder: The cylindrical housing containing the key plug, pins (or discs/wafers), and springs in a pin tumbler lock. The plug rotates within the cylinder when the correct key is inserted. The cylinder lock was popularized by Linus Yale Jr. in the 1860s and became the dominant padlock mechanism in the 20th century.

D

Dead Lock: A lock in which the bolt can only be moved by a key — it does not spring back automatically. Contrasted with a spring latch which closes automatically. Most padlocks are deadlocking by design.
Detective Lock: See Detector Lock. — See also: Detector Lock
Detector Lock: A lock fitted with a mechanism that registers if an unauthorized key or pick has been inserted. The detector trips when a wrong key is used, and can only be reset with the correct key. The Chubb Detector Lock (1818) was the most famous example; famously picked by A.C. Hobbs at the 1851 Great Exhibition.
Disc Tumbler: A locking mechanism using flat rotating discs instead of pin stacks. Each disc has a notch; when the correct key rotates all notches into alignment, the shackle is released. Used in Scandinavian/Polhem-style padlocks and some modern locks. Also called a rotary disc mechanism.
Dog (Locking Dog): A hardened steel component inside a padlock body that engages the shackle leg(s) to hold it locked. In ball-bearing designs, the locking dogs are steel balls. The term is common in American padlock manufacturing nomenclature.
Double-Bitted Key: A key with bit profiles on both sides, or a key cut on both edges. On railroad switch keys, double-bitted keys operate locks requiring cuts on both sides of the key blade. Compare to single-bitted.
Double Locking: A padlock with two separate bolts that lock both the heel and the toe of the shackle simultaneously. Also called heel-and-toe locking. Provides significantly greater resistance to forced entry than single-bolt designs.

E

Eight Lever: A padlock mechanism with eight lever tumblers, requiring a key that lifts all eight levers to the precise height to retract the bolt. More secure than four or six lever designs. The eight lever category includes both single-bitted and double-bitted variants.
Express Padlock: A padlock made specifically for use by express companies — Adams Express, American Express, United States Express, and similar carriers — to secure shipments, mail bags, and freight. Express padlocks often bear the carrier's name or initials as a marking. A major collecting category with hundreds of distinct varieties.
Extruded Body: A lock body formed by forcing metal through a die to create a consistent cross-sectional profile, then cutting to length. Extruded brass bodies became common in the mid-20th century. Lighter and more economical than cast bodies, but less collectible.

F

Fetterlock: A simple antique padlock with a large arched shackle and ward springs, historically used to hobble livestock (cattle and horses) as well as for securing goods. Common through the 19th century. The term also appears as a heraldic charge.
Figural Padlock: A padlock whose body is cast or formed in the shape of a figure, animal, object, or decorative motif — rather than the standard rectangular or disc body. Chinese figural padlocks are a prominent category; Western examples include fish, owls, animals, and human figures.

G

Gallery Lock: A lock displayed in a collection as an example of a specific type or rarity, rather than for active use. On this site, gallery listings represent archive entries for research and documentation purposes.

H

Hardened Shackle: A shackle that has been entirely heat-treated for maximum cut resistance. Contrasted with a case-hardened shackle (only the outer surface is treated). Advertised on many railroad and high-security padlocks from the late 19th century onward.
Hasp: A hinged metal strap with a slot that passes over a staple; the padlock shackle is then inserted through the staple to lock the hasp closed. Hasps are the primary hardware used with padlocks on doors, chests, and gates.
Heart Lock: A padlock with a cast heart-shaped body, popular throughout the 18th and 19th centuries. Heart locks typically used lever mechanisms. Variants include half-heart and iron heart designs.
Heel: The fixed or retained leg of the shackle — the side that remains permanently inserted in the lock body. Contrasted with the toe, which is the free leg that releases when unlocked.
High Security Padlock: A padlock engineered to resist picking, drilling, cutting, and other attacks. Characteristics include hardened steel bodies, anti-pick pins, ball-bearing locking dogs, restricted keyways, and shrouded shackles. Notable makers include Sargent & Greenleaf, Master Lock (high-security lines), ABUS, and BEST.

I

Indicator Lock: A padlock featuring a visible counter or indicator that records how many times the lock has been opened. Used by express companies and the military to detect unauthorized entry. The counter increments with each opening and cannot be reset without the proper key. Also called a counter padlock.
Integrated Mechanism: A locking mechanism in which the tumblers directly engage the shackle, without an intermediate actuator. Scandinavian-style rotating disc locks and lever padlocks with integral bolt-lever are examples. Older than modular designs; padlocks with integrated mechanisms typically require the key to re-lock them.

J

Johnson Rotary Lock: A padlock design using a rotating cylindrical plug mechanism patented by the Johnson company. A distinct sub-category in the archive; Johnson Rotary Locks are identified by their unique barrel-like opening mechanism.

K

Key Retaining: A design in which the key cannot be removed while the lock is open — preventing the lock from being left open accidentally. Common on high-security and institutional padlocks.
Keyed Alike: Multiple padlocks that share the same key cut — one key opens all of them. Used in facilities where one person needs access to many locks. Abbreviated KA.
Keyed Different: Each padlock in a set has a different key — no key opens another lock in the set. The standard configuration for retail padlocks. Abbreviated KD.
Keyway: The opening in the lock cylinder through which the key is inserted. The keyway profile (the shape of the opening and its internal projections called wards) is designed to accept only specific key blanks. Restricted keyways are harder to duplicate.

L

Laminated Body: A padlock body constructed from multiple layers of flat steel plates riveted together. Laminated padlocks became widespread in the early 20th century as a cost-effective alternative to cast bodies. Master Lock popularized the laminated design.
Lever Tumbler: A flat metal plate (lever) pivoting on a post inside the lock. Each lever must be raised to a precise height by the key before the bolt can move. More levers = more security. The lever mechanism was the primary security standard from the 18th century until the widespread adoption of the pin tumbler cylinder. Six and eight lever locks are common antique collecting categories.
Locking Dog: See Dog. — See also: Dog
Long Shackle: A padlock shackle with a greater clearance height than the standard shackle, allowing it to pass through thicker chains, hasps, or staples. Abbreviated LS.

M

Master Key: A key cut to open every lock within a master-keyed system, each of which also has its own individual change key. Used in facilities requiring tiered access control.
Master Keyed: A lock that can be opened by both its own individual key and a master key. Padlocks sold for institutional use are commonly master keyed.
Military Padlock: A padlock produced under contract for military use, bearing government inspection marks, contract numbers, or branch insignia. Military padlocks are a major collecting category; documented variants represent dozens of contractors and hundreds of distinct models.
Modular Mechanism: A locking mechanism in which the tumblers do not directly engage the shackle. Instead, the tumblers rotate a plug, which via an actuator moves a bolt or locking dog to release the shackle. Pin tumbler cylinders use modular mechanisms. Allows for key-retaining designs and simplifies rekeying.

N

NOS: New Old Stock — a padlock that has never been used and retains its original finish, often still in its original box or packaging. NOS examples are highly prized by collectors for their condition and documentation value.

O

Original Key: The key that was sold with or made for a specific padlock at the time of manufacture. Padlocks retaining their original key command a premium in the collector market.

P

Pancake Padlock: A flat, disc-shaped padlock body — resembling a pancake in profile. Pancake padlocks typically use a push key (spring mechanism) and were widely produced from the mid-19th century through the early 20th century. A major collecting category on this site, with nearly 700 documented examples.
Pin Tumbler: The dominant lock mechanism of the 20th century, invented in its modern form by Linus Yale Jr. (1861). A series of spring-loaded pin stacks — each consisting of a key pin and a driver pin — are pushed down by springs. The correct key lifts each pin stack to the precise height where the gap between key pin and driver pin aligns with the shear line, allowing the plug to rotate.
Plug: The rotating inner cylinder of a lock, into which the key is inserted. The plug rotates inside the outer cylinder (shell) when the correct key aligns the tumblers. The back of the plug typically has a cam or actuator that moves the bolt.
Polhem Lock: See Scandinavian Padlock. — See also: Scandinavian Padlock
Post Key: A key with a solid cylindrical shank and a projecting bit or wing, designed to operate lever locks. The post (shank) is inserted into the keyway over a central post in the lock, and the bit engages the levers. Common on older padlocks and furniture locks.
Postal Padlock: A padlock produced under contract for the United States Postal Service or other postal systems to secure mail pouches, bags, and facility doors. Postal padlocks bear USPS contract marks and are a prominent collecting category.
Push Key: A key operated by pushing it straight into the keyway and pressing, rather than rotating. Used in spring-loaded padlocks (pancake, smokehouse, and screw types). The key depresses internal springs that hold the shackle locked. Also called a spring key.

R

Railroad Padlock: A padlock produced for use by railroad companies to secure switch locks, car doors, toolboxes, depots, and other railroad infrastructure. Railroad padlocks bear the reporting mark or name of the railroad; hundreds of distinct railroads are documented in this archive.
Rarity Rating: A collector's assessment of how uncommon a specific padlock variant is. On this site, ratings run from Common (widely available) to Uncommon, Scarce, Rare, and Very Rare (fewer than a handful of known examples). Rarity reflects both survival rate and original production volume.
Reporting Mark: The standardized letter code assigned to a railroad company by the Association of American Railroads (AAR), used to identify ownership of rolling stock and equipment. Reporting marks are commonly stamped or cast on railroad padlocks and switch keys (e.g., UP = Union Pacific, B&O = Baltimore & Ohio).
Restricted Keyway: A keyway profile controlled by the manufacturer — blanks are not sold through retail channels and can only be duplicated by authorized dealers. Prevents unauthorized key copying.

S

Scandinavian Padlock: A padlock type with a cast iron body loaded with a stack of rotating discs. Invented by Swedish engineer Christopher Polhem (c. 1700) and widely produced from the mid-19th century. The key rotates each disc until all notches align with the shackle, allowing it to slide free. Also called a Polhem lock or American lock (after the American Lock Co., which made them until the 1950s). Extremely resistant to picking.
Screw Padlock: A padlock in which the shackle is released by screwing (rotating) it rather than pulling it out. A screw key compresses internal springs to retract the bolt. An older design, predating the lever and pin tumbler mechanisms.
Seal Lock / Seal Padlock: A padlock designed to accept a wire or cable seal threaded through the shackle loop, used to indicate whether a container or vehicle door has been opened since last inspection. Common on railroad freight cars, truck trailers, and utility meters.
Shackle: The looped, U-shaped member of a padlock through which a hasp, chain, or bar passes. The shackle is typically round or square in cross-section. Key terms: heel (fixed side), toe (free side), clearance (inside height of the loop), diameter (thickness of the shackle steel).
Shear Line: In a pin tumbler cylinder, the boundary between the rotating plug and the fixed cylinder body. When the correct key raises each pin stack so the gap between key pin and driver pin sits exactly at the shear line, the plug can rotate freely.
Shroud: A protective collar or housing around the shackle that limits exposure of the shackle legs, making bolt-cutter attacks more difficult. Shrouded padlocks are sometimes called closed-shackle or guarded-shackle locks.
Six Lever: A padlock with six lever tumblers. Six lever locks were the British and European security standard for much of the 19th and 20th centuries; BS 3621 (British Standard for lock security) requires six levers minimum. A significant antique collecting category.
Skeleton Key: A key with much of the bit filed away so that it passes over all ward obstructions and can open many warded locks. Also called a pass key or in Latin, clavis adultera. Not effective against lever or pin tumbler locks.
Smokehouse Padlock: A large, simple antique padlock used on smokehouse doors and similar agricultural structures. Typically uses a push key or warded mechanism. A recognized collecting category noted for their utilitarian construction and variety of markings.
Spring Padlock: A padlock that locks automatically when the shackle is pushed closed — the shackle snaps into the locked position under spring pressure, without requiring the key. Also called a snap lock or spring shackle padlock. The key is needed only to open the lock.
Stamped Body: A padlock body formed by pressing flat sheet metal between dies. Stamped bodies were cheaper and faster to produce than cast bodies; adopted widely by American manufacturers from the 1870s onward. The Adams & Westlake stamped switch lock (patented 1908) transformed the railroad padlock market.
Story Lock: A padlock with a documented provenance or notable history — a lock associated with a famous person, event, or location. Story locks command significant premiums at auction. Also a formal collecting category on this site.
Switch Key: A key used to operate a railroad track switch lock — a padlock securing the mechanism that moves a section of rail to direct trains from one track to another. Switch keys are highly collectible, with markings identifying the railroad, manufacturer, and sometimes the specific division or depot. The sister archive to this site (RailroadSwitchKeys.com) is dedicated to their documentation.
Switch Lock: The padlock installed on a railroad track switch stand to prevent unauthorized or accidental throwing of the switch. Switch locks are a subset of railroad padlocks and are typically marked with the owning railroad's name or reporting mark.

T

Talon: The projecting part of the bolt in a lever lock, which passes through a slot in the levers as the bolt moves. The levers must be lifted to the correct height to allow the talon to pass.
Toe: The free leg of a padlock shackle — the side that releases from the body when the lock is opened. Contrasted with the heel, which remains retained in the body.
Transportation Lock: A padlock produced for securing transportation infrastructure and vehicles — including railroad cars, trucks, buses, aircraft, and shipping containers. A broad category encompassing express, postal, railroad, and carrier locks.
Trick Padlock: A padlock designed to puzzle or challenge — it may appear to have no keyhole, open by a non-obvious action, or require a sequence of manipulations. Trick and puzzle locks are a long-standing collecting category appealing to those interested in mechanical ingenuity.
Tumbler: Any internal component whose movement by the correct key allows the lock to open. The term encompasses levers, pins, discs, and wafers — collectively the security elements that must be aligned for the bolt to retract.

V

Variation: A documented variant of a padlock model — differing in shackle size, body finish, markings, or mechanism detail from the standard type. Collectors assign variation numbers or codes (e.g., 2.1, 2.2) to distinguish between subtypes of the same lock.

W

Wafer Tumbler: A simplified tumbler mechanism using flat metal wafers (rather than stacked pins) as the security elements. The correct key aligns all wafers so the plug can rotate. Wafer locks offer less security than pin tumbler locks; common in low-cost padlocks and cabinet locks.
Ward: A fixed obstruction inside a lock or keyway that blocks all keys except those cut to pass it. Wards are the oldest lock security feature; a warded lock relies entirely on wards for security. A skeleton key bypasses wards by having all ward-blocking portions removed.
Warded Lock: A lock that uses only wards (fixed obstructions) as its security mechanism. Warded padlocks were among the earliest mass-produced padlocks; widely used through the 19th century. Limited security by modern standards, but produced in extraordinary variety and quantity. Two major collecting sub-categories: warded pancake and warded other.

Latin & Historical Terms

Latin: catena: Chain, fetters. Root of the English word "chain."
Latin: claudo (clausus): To confine, shut up, close, blockade, besiege.
Latin: claustrum: Lock, bolt, bar, prison, den, pen, enclosure. Root of "cloister."
Latin: clavis: Door key. Root of "clavicle" and related English words.
Latin: clavis adultera: False or skeleton key. A key cut to bypass wards.
Latin: obfirmo: To bolt, lock, fasten, bar.
Latin: sera: Movable bar or bolt.
Latin: sera pensilis: Padlock — literally "hanging bolt." The Roman term for a padlock.

Padlock Glossary