Guides · 2026-10-08 · 5 min
Master key basics for small-building landlords
How a master key system works, what it is worth, and what to ask for before it is installed.
What a master key does
A master key system lets one key open many locks, while each lock still has its own key that opens only that lock. For a landlord, that means you hold one key for all the apartment doors and each tenant holds one for theirs.
Why it helps
When a tenant leaves, you rekey one apartment lock. The other tenants and your master key are not affected. You carry fewer keys and you can show exactly who holds what.
It also gives you a clear way to handle common doors: the street door, the basement and the roof can be on a separate group of keys that each tenant receives.
What to ask for
Ask for a written chart showing which keys open which locks. Ask whether copies of the master key are restricted, so they cannot be duplicated at any key shop. Ask whether more locks can be added to the system later.
A system with no chart is hard to maintain, so do not skip the paperwork.
From Montrose Locksmith, a mobile locksmith and intercom company based in East Williamsburg, Brooklyn. Questions about your door or entry system? (929) 249-5806.