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Commercial & Residential Keyway Identification

Keyway warding determines which pick profiles, decoders, and blanks can access the internal cylinder plug. Recognizing keyway profiles in the field allows operators to immediately determine pin clearance, identify master-keyed multiplex architectures, and select appropriate key blanks.

Keyway Taxonomy & Geometry​

Lock cylinders use specific warding profiles designed to prevent unauthorized key entry and restrict pick manipulation:

Open Keyways (e.g. KW1, M1)
  - Straight, wide open keyway channel
  - Accepts standard 0.025" picks and wide tensioners

Paracentric Keyways (e.g. SC1, Y1, Sargent LA)
  - Curved warding extending past the vertical centerline
  - Requires navigating around shelves; best suited for 0.020" or 0.015" picks

Multiplex Keyways (e.g. Schlage Obverse/Reverse, Corbin Russwin System 70)
  - Hierarchical family tree of milled profiles
  - Sub-master and grand-master keys bypass multiple individual cylinder profiles

Restricted / Patented Profiles (e.g. Medeco, Schlage Primus, Assa Twin)
  - Secondary locking sidebars, angled cuts, or factory-controlled distributions

Schlage Classic Multiplex System​

Schlage's classic commercial architecture utilizes a sophisticated multiplex keyway structure. In a multiplex system, individual sub-level keyways are milled with specific warding projections, while higher-level master keys have thinner profiles that bypass multiple individual cylinder keyways.

Obverse Key Hierarchy​

The primary commercial series is the Obverse family:

TierProfile DesignationsFunction & Access Scope
All-Section MasterHEnters all Obverse cylinders (C, CE, E, EF, F, FG, G)
Multi-Section Sub-MasterC-EEnters cylinders keyed with C, CE, and E keyways
Multi-Section Sub-MasterE-GEnters cylinders keyed with E, EF, F, FG, and G keyways
Multi-Section Sub-MasterC-GEnters all standard single-section cylinders
Single-Section Change KeysC, CE, E, EF, F, FG, GIndividual operating keys; enter only their matching cylinder plug
Universal PlugU KeywayA broached cylinder plug designed to accept all Obverse keys (C through H)
                  [ H ] (All-Section Master Key)
                 /     \
         [ C-E ]         [ E-G ] (Multi-Section Sub-Masters)
        /   |   \       /   |   \
     [ C ] [ CE ] [ E ] [ EF ] [ F ] [ FG ] [ G ] (Single-Section Keys)
        \   \     \   /   /     /     /
         \---\-----\-/---/-----/-----/
                      |
              [ U Keyway Plug ] (Accepts All Obverse Keys)

Reverse Key Hierarchy​

Schlage also manufactures a mirrored Reverse keyway family to prevent crossover between separate facilities or departments within large institutions:

TierReverse ProfileObverse CounterpartScope
All-Section MasterLHEnters all Reverse cylinders (D, DQ, Q, QS, S, ST, T)
Multi-Section Sub-MasterD-QC-EEnters D, DQ, and Q keyways
Multi-Section Sub-MasterQ-TE-GEnters Q, QS, S, ST, and T keyways
Single-Section Change KeysD, DQ, Q, QS, S, ST, TC, CE, E, EF, F, FG, GIndividual operating keys
Universal PlugZ KeywayU KeywayAccepts all Reverse keys (D through L)

American Lock Keyway Taxonomy​

American Lock padlocks and commercial utility cylinders use an interlocking set of model numbers, blank references, and factory designations that frequently cause confusion in the field:

Common DesignationManufacturer / Blank NamePin CountCross-ReferencesProfile Characteristics
AM3American Lock AK55-PinIlco 1045, JET AM6Standard commercial profile (PTKB1 base profile)
AM4American Lock AM45-PinJET AM6LLong neck version of AM3; clears protective shackle shrouds
AM5Original Lishi Tool——Not a key blank; tool model designation for decoding 5-pin American locks
AM6Curtis / Hillman / JET5-PinIlco 1045Legacy distributor designation for AM3
AM7American Lock AK66-PinIlco A1045, JET AM7Standard 6-pin version of the PTKB1 profile
PTKB1American Lock Factory Profile5/6-PinAK5 / AK6Base standard profile across commercial padlocks
PTKB2Narrow Blank Profile5/6-Pin—Narrowed warding profile for tighter security housings
PTKB748Restricted Blank5/6-Pin—Factory-restricted profile for proprietary commercial installations
R7Reverse Restricted5/6-Pin—Direct mirror reverse of the PTKB748 profile

Ubiquitous Heavy Equipment & Fleet Keys​

In physical assessments of industrial, infrastructure, construction, and commercial facilities, heavy equipment keys often provide unintended bypasses to exterior gates, vehicle cabs, and perimeter enclosures:

Equipment / SystemKey Code / MarkingBlank ReferenceCommon Applications
Caterpillar5P8500Ilco 1600 / CAT 5P8500Ubiquitous across Caterpillar excavators, loaders, dozers, padlocks, and site gates
John DeereJD Commercial / AT195302Ilco 1430John Deere compact loaders, backhoes, skid steers, utility vehicles
Komatsu787Ilco 1680Komatsu heavy earthmovers, industrial equipment, site generators
Case / BobcatD250 / Bobcat StandardIlco 1642Bobcat skid steers, mini-excavators, Case tractors, Ingersoll Rand equipment
Pollak / Universal1107 / Ford TractorIlco 1500Industrial ignition switches, yard tugs, commercial perimeter forklifts

Ilco Key Blank Directory Cross-Referencing​

When identifying unknown blanks in the field, use the industry standard cross-reference indices published in the Ilco Key Blank Directory:

  • North American Cylinders (Part 04): Indexes commercial architectural cylinders (Schlage, Sargent, Yale, Corbin Russwin, Falcon, Dexter, Weiser, Weslock, Arrow).
  • Vehicular Key Directory (Part 03): Indexes automotive, truck, and commercial vehicle ignitions and door locks.
  • Cross-Reference Table (Part 12): Provides direct translation across competing aftermarket manufacturers:
    • Ilco (e.g., 1045 / A1045)
    • Curtis (e.g., AM3 / AM7)
    • Dominion
    • ESP
    • Jet (e.g., AM6 / AM7)
    • Star
    • Taylor

Authoritative References & Online Catalogs​