Cylinders & Keys5 min read28 February 2026

Master key systems: how does a key plan work?

A hierarchical key plan determines who can open which door. Ideal for apartment buildings, businesses and care facilities. We explain the structure step by step.

key planmaster keyapartment buildings

What is a key plan?

A key plan is a hierarchical system in which one master key opens every door, while an individual key opens only its own door(s). This way, the building manager of an apartment block has access to all technical rooms, while residents cannot enter each other's flats.

The three levels in a typical plan

Level 1 — Master key: opens all doors in the system. Level 2 — Group key: opens a cluster (e.g. the second floor). Level 3 — Individual key: opens only one door or a limited set of doors. Further subdivisions are possible for larger buildings.

Patented keys and copy protection

In a professional key plan, all keys are patented. Duplicates can only be produced by a certified locksmith with written authorisation from the owner. This prevents residents or former employees from having unauthorised duplicates made.

When do you need a key plan?

Apartment buildings with more than 4 units, businesses with multiple departments, care facilities and hotels all benefit from a key plan. It simplifies management, reduces costs when staff turnover occurs, and drastically increases security.

Frequently asked questions

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