A master key system is designed so that individual keys open only their assigned door, while a master key opens a defined group of doors, and a grandmaster key may open every door across a whole property. Apartment communities and HOAs use these systems so maintenance staff can access multiple units while individual residents retain a key that opens only their own door.
On a real property, the system's security depends entirely on controlling who holds each level of key; a lost or uncontrolled master key compromises every door beneath it in the hierarchy, not just one unit. Re-keying an entire master system after a serious loss is expensive and disruptive, which is why key control procedures matter as much as the lock hardware itself.
Aftermarket key duplication is a common failure mode — many standard keys can be copied at any hardware store unless the property uses a patented, restricted keyway that limits duplication to authorized locksmiths. Worn cylinders and outdated records of who was issued which key level also erode the system's reliability over time.
In a patrol program, officers do not typically hold master keys but may notice and report signs of unauthorized access such as damaged locks, and property managers should keep a written key control log tracking who holds which level of key, updated whenever staff or vendors change.
Related entries
Official sources
- [1]GSA Federal Specification for key control (reference)U.S. General Services Administration
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