How a Master Key System Works (And Why Denver Businesses Need One)
Plain-English guide to commercial master key systems for Denver businesses — how they're built, what they cost, and how to keep them secure as employees turn over.
By Andrew — Master Locksmith, Denver Colorado Locksmith 247
If you manage a Denver office, retail location, restaurant, or multi-unit property, you've probably wrestled with this: the manager needs every door, the night shift needs three, the cleaner needs two, and the owner needs all of them — including the safe. Handing out individual keys creates a giant ring on every belt and a security mess at every termination.
That's what a master key system solves.
The basics in 60 seconds
Every door still has its own unique "change key." But each cylinder is pinned so that one or more master keys also open it. Common levels:
- Change key (CK): opens one door.
- Master key (MK): opens a group of doors — e.g. "all front-of-house."
- Grand master (GMK): opens every door in the building.
- Great grand master: spans multiple buildings (used by property managers).
A realistic Denver example
A 12-door medical office we did last year in Cherry Creek:
- Each provider got a change key to their own office only.
- The front desk got a master that opens reception, supply, and breakroom.
- The office manager got a master that opens everything except the controlled-substance cabinet.
- The owner got the grand master.
Total install for new cylinders, keys, and the schema: about $1,400 — less than the cost of one botched termination and emergency rekey.
The trade-off no one tells you
Master-keyed cylinders have extra pins, which makes them statistically easier to pick than a standard cylinder. For most Denver businesses that's a non-issue — bad actors smash glass or pry doors, they don't pick locks. But if you store cash, controlled substances, or sensitive data, ask for:
- Restricted keyway hardware (Medeco, Mul-T-Lock, ASSA) — keys can only be cut at one authorized dealer with your signature on file.
- Patented keyways with a 10–20 year duplication patent so big-box stores can't copy them.
Keep the system secure over time
- Get a key control log. Who has which key, when they got it, when they returned it. We provide a free template with every install.
- Rekey on turnover, not "eventually." The hour after you fire someone is the wrong time to discover four people share that master.
- Audit annually. Walk every door, try every key, reconcile the log.
When to skip master keying and go electronic
If you have 30+ doors, frequent turnover, or compliance requirements (HIPAA, PCI), an access control system pays for itself fast. You disable a fob in 5 seconds instead of rekeying 20 cylinders. We design and install both — and often a hybrid where exterior doors are electronic and interior offices stay mechanical. Learn more on our commercial locksmith page.
Get a free walk-through
We offer no-charge on-site assessments for Denver-area businesses. We'll map your doors, talk through who needs access to what, and quote two or three options. Call (720) 575-4013 or request a visit.
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