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A master key system allows one key to unlock many doors and each door has its own key as well. There is a single word for what a master key system is. Arizona takes master keys seriously. ARS 13-1505 groups master keys with burglary tools and exempts people who use them in lawful business. Old Glory Locksmith sets up and services these systems for Phoenix Valley companies.
Our commercial locksmith services cover rekeying and lock installation and lockout response. Owner Cory Bahr does the work himself. Owners usually ask one thing first. Do we need this or just more keys? This guide covers the master key benefits and the real risks and the Arizona details most national guides skip.
One rule sits above every key plan. Under 29 CFR 1910.36 employees must be able to open an exit door from the inside at all times without keys or tools or special knowledge. A master key system for business use never replaces that.
What Is a Master Key System?
A master key system is a system of locks and keys that are designed in a hierarchy. There are many locks opened by one key at the top and there is one key at the bottom for each lock. Every lock in the set accepts at least two keys. The change key opens that single lock. The master key opens every lock in the group.
Inside a pin tumbler cylinder the locksmith adds extra master pins. Those pins let a second key reach the shear line. A master key looks like any other key. Only its cuts differ.
How Master Key Systems Work Step by Step
A locksmith pins every cylinder to accept two keys and then records the codes. Here is how master key systems work from first walk to final test.
Walk the site
Count every door and note who needs which ones.
Draw the schematic
This chart maps each key level like a family tree. Changes cost little until the cylinders get ordered.
Pick the hardware
Brand and keyway set the real security level. A restricted keyway limits who can copy keys.
Pin the cylinders
Master pins let the change key and the master key both line up.
Cut and stamp the keys
Each key gets a code that matches its door or group.
Test and record
Try every key in every door. File the bitting codes so a future key never repeats one.
What Are the Levels in a Commercial Master Key System?
Most commercial master key system designs use four levels. A fifth is added to large campuses.
| Level | Opens | Usual holder |
|---|---|---|
| Change key | One door or room | Tenant or employee |
| Sub master | One group such as a department | Department lead |
| Master | Every door in a zone or building | Manager or owner |
| Grand master | Several zones or buildings | Owner or facilities lead |
| Great grand master | Every lock in the system | Owner only |
Fewer levels mean a tighter system. Each added level puts more keys in more hands that open more doors. Some owners never cut the top key at all. It has to exist on paper because of how the codes work.
Doors can also be keyed alike so one key fits several closets. Keyed different means a lock takes only its own key.
Master Key Benefits for a Business
The biggest master key benefits are fewer keys better access control and quicker checks. One manager has only one key, not 30. Fewer keys in circulation also means fewer lost ones. A lost change key exposes one door. Cleaning crews and maintenance staff can reach the zones they need and nothing else.
Mechanical locks keep working through a power outage. No wiring and no software are involved. Expansion works only if the plan builds it in from day one. What is a master key system actually buying you? Mostly time. Nobody hunts through a ring for the right key.
Do You Need a Master Key System for Business Use?
Use one when people are going to various doors. It is not required when everyone has their own single key ring. A system pays off in places like these:
- Multi tenant buildings where a landlord needs the common areas
- Medical and dental offices with supply rooms and records rooms
- Warehouse suites that share a yard gate
- Churches and schools and clubhouses with many volunteers
Skip it in these cases:
- A shop with one door and three employees. A simple rekey costs less
- Sites that need a record of who entered and when. A metal key keeps no log. Electronic access control fits better there
We tell owners this on the phone. A system you do not need is money wasted.
How Strong Is Master Key Security?
Master key security is okay if the plan is good and is poorer in quality than individual keying. A master keyed cylinder is one that contains more than one keying location. The math shows why. A six pin cylinder with two shear points per chamber can accept up to 64 different keys. A 2003 paper in IEEE Security & Privacy by Matt Blaze went further. It showed that one master keyed lock and its change key plus spare blanks can be enough to work out the master for the whole system.
The honest answer to “what is a master key system giving up?” is some resistance to picking and to key making attacks. You can win much of it back:
- Choose a patent protected keyway so only authorized dealers cut keys
- Keep the number of levels low
- Upgrade exterior cylinders to high security cylinders first
- Use two cylinders per door where the risk justifies the cost
What Should Phoenix Valley Businesses Know About Master Keys?
Here are the key factors Phoenix Valley businesses should consider when planning and maintaining master key systems.
- Arizona law
ARS 13-1505 names locksmiths and key makers and vehicle dealers and law enforcement in its exemption. It does not hand every key holder a free pass. A written record of who holds what shows a lawful reason. Ask an attorney about specific cases.
- Phoenix heat and dust
Phoenix logged 31 straight days at or above 110 degrees in July 2023 according to the National Weather Service. Exterior cylinders take a beating from that heat and from fine desert dust.
- Key and cylinder maintenance
A stiff cylinder tempts staff to force the key and a bent master key means a rekey call. Book a cleaning and lubrication check before summer.
- Crime trends
Crime numbers are falling. The Bureau of Justice Statistics reported property offenses down 9 percent in 2024. Falling crime does not fix a key nobody can account for.
- Service area
Old Glory works out of Glendale and reaches Phoenix and Peoria and Surprise and Avondale and Goodyear and Buckeye. We also cover Tempe and Mesa and Chandler and Scottsdale and Gilbert.
- Tenant turnover
Strip centers and warehouse suites and office parks across those cities share one problem. Tenants turn over faster than keys get collected.
- Shared access
Shared doors like a mail room can use a maison key system where every tenant key opens the shared lock. Private doors still need their own keys.
How Does Business Key Management Work?
Business key management is a single written record of each key and the person who holds it. If you do not have that record then it is just a large key ring. Planning for business security after an employee leaves also means collecting issued keys, updating access records, and arranging rekeying if a master key is not returned.
- Stamp and number every key
- Keep a signed log for each key issued and returned
- Lock the top level key away in a safe
- Collect keys at every exit interview
- Review the log every quarter
- Call for commercial rekeying the day a master key goes missing
Never copy a master key at a hardware store. Restricted key blanks reach only registered dealers and that is the point. Unauthorized key duplication wrecks the whole plan.
Tips and Takeaways Before You Call a Locksmith
| Tip 1: Walk every door before you price anything. A door missed now costs more to add later. |
|---|
| Tip 2: Cap the levels. Three levels beat five when the building allows it. |
Key takeaways
- What is a master key system? A hierarchy where one top key opens many locks and each bottom key opens one.
- It trades some pick resistance for convenience and a good keyway wins much of it back.
- Exit doors must open from inside without keys under OSHA rules.
- Records protect you more than hardware does.
| Pro tip: Ask for the schematic in writing before any key gets cut. A locksmith who cannot show the chart cannot prove which key opens what. |
|---|
Frequently Asked Questions
Is a master key illegal?
No. Master keys are legal for lawful business use. ARS 13-1505 targets burglary tools and names master keys with an exemption for lawful trades. Using one to enter a place you have no right to enter is a crime. This is not legal advice.
How much does a master key system cost?
Cost depends on door count and cylinder grade and the number of key levels. Restricted high security keyways cost more than standard ones. Old Glory prices every job after a site walk. Call 602 696 0763 to book one.
What are the downsides of using a master key?
Extra shear points make picking easier and a lost master exposes every door it opens. Expansion is hard unless the plan built it in. Rekeying a compromised system costs more than rekeying one lock.
Can you get a master key for all locks?
No. A master key works only on locks pinned into its system. Older locks can join if their cylinders match the keyway or get replaced. A locksmith rekeys or swaps cylinders to bring them in.
Can a master key open any door?
No. It opens only the doors in its zone of the system. A master key for your building does nothing on a stranger’s door.
Can I copy a Master Lock key at Home Depot?
Master Lock is a padlock brand and not a master key. Many standard padlock keys use common blanks that a store may copy. Keys stamped Do Not Duplicate or cut on restricted blanks need authorization. Store policy varies so ask first. Never copy a system master key at a store.
What kind of key can never unlock a door?
A key with the wrong cuts or the wrong keyway for that lock. An uncut blank never turns a pinned cylinder. Inside a system a change key never opens any door but its own.
Is there a universal master key?
No. No single key opens every lock from every brand. The closest thing is the great grand master and it opens only the locks inside one system.
Are master locks hard to break?
It depends on the model. Laminated steel padlocks with thin shackles fall to bolt cutters. Hardened shackles and shrouded bodies resist far better. No padlock stops a determined thief with time so pair it with a solid door and good lighting.
Your Next Step
You now have the answer to what is a master key system and whether your business needs one. A site walk turns that answer into a plan. Call Old Glory Locksmith at 602 696 0763 and ask for our commercial locksmith services team.
Old Glory is veteran and family owned and has served the Phoenix Valley since 2011. We hold an A+ rating with the Better Business Bureau and a 5 star average across more than 150 Google reviews. We are open 24 hours at 6751 N Sunset Blvd #320, Glendale AZ 85305.