Master Keying
David M. Koenig, CPP
Master Keying Is...

System Of Organizing Numbers
– For Cutting Keys
– For Pinning Locks
Grouping Of Locks And Keys
 Set Of Locks That Are Operated By More
Than One Key

Master Keying Provides
Convenience Over Security
 Separate Keys For Individual Locks
 Keys To Operate Groups Of Locks
 Single Key For All Locks In System
 Ability To Carry Fewer Keys
 Organization Of And Management OF
Lock & Key System

Master Keying
Disadvantages
Makes Locks Easier To Pick
 Small Master Pins Increase Service Issues
 Higher Re-keying Cost If GMK Or GGMK
Keys Are Lost
 More Thought Involved In Administration
 Controlled Destruction of Lock Security

Master Keying Terms
KA - Keyed Alike - Several Locks Operated
By The Same Key
 KD - Keyed Different - Each Lock
Operated By It’s Own Key

Master Keying Terms

CK - Change Key
– Work Individual Lock
MK - Master Key
 GMK - Grand Master Key

– Works Large Group Of Locks

GGMK - Great Grand Master Key
– Fits All Locks In System
Master Keying Terms

SKD - Single Keyed Different
– Lock Set To Change Key Only

NMK - Not Master Keyed
– Similar To SKD

Levels - Number Of Different Types Of
Keys In System
– Example CK-MK-GMK = 3 Level System
Master
Keying
Terms
1

Sectional Keyways - Variety Of Key Blank
Grove Sizes And Shapes
– Divided Into Groups
– Some Patterns Are Wider Than Others
– Higher Level Patterns Fit Into Multiple
Keyways
– Allows Cut Numbers To Be Repeated
System Size and Security
5 Or 6 Pin Chambers (more is better)
 Chamber Depths
 Pinning Increment (Key / Pin Wear)
 How Many Chambers Are Progressed
 Angles (Or Other Factor) Employed

System Size and Security
MACS (Maximum Adjacent Cuts) Loss
 How Many Masters Employed
 Sectional Keyways

Typical System Example
8 Depths (1-10 Less Two for MK)
 Less Increments of Two
 Used In 6 Chambers Equals…
 4 To 6th Power Equals…
 4,096 Theoretical Combinations
 Less MACS Of 20%
 Equals 3,276 Maximum Combinations

Medeco Biaxial System Size
4 Depths (1-5 Less One Number For GMK)
 Used In 6 Chambers Equals…
 4 To 6th Power Equals…
 4,096 Theoretical
 Times 9 Sections (Angles) Equals...

Medeco Biaxial System Size
Equals 36,864 Changes Under Single MK
 With MACS Loss Of 20% Combinations
(Maximum Adjacent Cuts)
 Over 29,400 Maximum Combinations
 Number Of Chambers Used For
Master Keys Reduces Maximum And
Determines Availability Within A MK
