A master key system is a hierarchical key arrangement where individual keys operate specific locks, while a master key can open all locks in the system. This provides both security and convenience for buildings with multiple access levels.
How Master Key Systems Work
In a standard pin tumbler lock, one key operates one lock. Master keying adds extra pin positions that allow two different keys to work:
- Change key: The individual key that opens only one specific lock
- Master key: Opens all locks in the system
- Sub-master key (optional): Opens a group of locks
- Grand master key (optional): Opens multiple master key systems
Who Benefits from Master Key Systems
Property Managers
Landlords and property managers can access any unit for maintenance while tenants have keys only to their own unit.
Businesses
Employees access their own offices while managers or owners can access all areas. Common areas may have keys that work for all employees.
Schools and Institutions
Teachers access their classrooms while custodial staff access all rooms. Administrators may have building-wide access.
Hospitals and Healthcare
Different departments have different access levels with administration having full access.
Types of Master Key Systems
Simple Master System
Two levels: individual keys and one master key. Best for small buildings.
Master and Sub-Master System
Three levels: individual keys, sub-masters for departments or floors, and one grand master.
Grand Master System
Four or more levels: individual, master, sub-master, grand master, and potentially great grand master.
Considerations and Limitations
- Each master level slightly reduces the security of individual locks
- Larger systems require careful planning
- Lost master keys compromise the entire system
- Professional design and installation is essential
Key Control
Maintaining control over master keys is critical:
- Limit the number of master keys issued
- Track all key assignments
- Use restricted keyways that cannot be copied
- Have a policy for lost keys
