Individual key (IK)
A individual key is a key that can only lock the cylinder for which it was made.
System keys are keys that can lock both the assigned own cylinder and also central cylinder. In systems with a central cylinder, these are referred to as individual keys.
Group key (GK)
In a General master key system (GMK-System), superordinate keys are referred to as group keys. Within a general master key system, a group key is a higher-level key for a specific area (locking group).
Main group key (MGK)
A main group key is defined within a General master key system a superordinate key, which can close several locking groups or hierarchy levels.
General master key (GMK)
A general group key is defined within a General master key system the key with the most authorizations. As a rule, it can open all cylinders in a GHS system. In rare cases, the area of use is slightly restricted for security slightly restricted for security reasons (e.g. server or cashier rooms).
Master key (MK)
A master key is within a Master key system the key, that can open all cylinders.
Cylinders in systems (manufacturer-dependent) are usually supplied with a certain number of keys. Additionally manufactured keys are then referred to as multiple keys.
Replacement key (also spare key)
Keys that are issued after delivery of a system, i.e. not in connection with the initial delivery, are treated as Duplicate key designated.