Specification Sheet

K E Y I N G S Y S T E M S
H O W T O S P E C I F Y M A S T E R K E Y I N G
6
The great grand master key is assigned the symbol GGM. The
rest of the symbols are the same as those in 3-level systems:
The GMKs are assigned single letters, e.g. A, B, C, D, etc. Caution:
Never use X for a grand master key due to the confusion which will
result with cross keying symbols presented an the next page.
Masters under each GMK are assigned two letters, the rst of
which is the same as its respective grand master key. Change key
numbers come after the letters. Changes under the grand (A1,
B1, etc.) and masters beyond AZ are handled exactly as in the 3
level system already described.
Changes directly under a grand are also handled as illustrated
in the 3-level system. For changes directly under the GGM with
no intermediate level masters, the change number is added directly to
GGM as shown by the example GGM1 in the schematic.
When locks are required which are not operated by ANY master keys or
other change keys in the system, they are referred to as “single keyed”
and given symbols SKD1, SKD2, etc.
When all higher levels of master keys are to be disallowed, sufx
(NMK) to the symbol of the key which is to operate. This means “not
master keyed” and can be applied to any level in the system. Cylinder
AA1(NMK) is operated by AA1 only. The AA master, A grand and
GGM are all blocked from operation. Cylinder AA(NMK) is operated
by the AA master only. Grand A and the GGM do not operate. Cylinder
A(NMK) would be operated by the A grand only, without the GGM.
4-Level Master Keying Systems
To Specify a Great Grand Master Key System (4 Levels of Keying)
Selective Master Keys
It is often useful in large keying systems to issue a high level
master key to maintenance personnel which allows access across
all master and grand master key boundaries of a keying system.
A selective master key is usually very close to the system’s top
master key, both physically and through its realm of access.
Nevertheless, it must be blocked from operating in many areas.
To designate that a lock be operated by a selective master key,
sufx the symbol in parentheses to the standard symbol. Example:
AA1 (ENG). This must be added every time the selective key is to
operate and left off whenever the selective key is NOT to operate.
For instance, you may lay out a system in which key AA1 is to
operate two different ofces. Inside one of them is an electrical
cabinet which must be accessible to maintenance personnel
carrying the ENG key. That lock must be specied as AA1(ENG)
while the lock for the other ofce must be specied as AA1.
Change keys directly under the selective key, such as ENG1, are
operated by all higher level keys, such as GGM.
Like cross keying, a selective master key is a convenience feature
which decreases the security of the cylinders it operates and
limits the expansion and exibility of the overall keying system.
The most common names and symbols for selective
master keys
ENG=Engineer’s key ATT=Attendant’s key
JAN=Janitor’s key HKP=Housekeeper’s key
GRD=Guard’s key MAIN=Maintenance key
GGM
A
AA AB
A1AB2AB1AA3AA2AA1 GGM1A1BB2BB1BA2BA1 SKD1
BBBA
B
BA1AB2AB1AA3AA2AA1 BA2 BB1 BB2
BBBAABAA
BA
GGM
ENG