Key takeaways
- Confirm property authorization and the exact openings in scope before cutting keys, rekeying cylinders, or releasing system information.
- An operating key opens assigned cylinders; a master key opens an authorized group; a control key removes and installs compatible interchangeable cores.
- SFIC and LFIC describe different core formats. Neither label identifies the keyway, hierarchy, or security policy by itself.
- A useful key hierarchy follows job roles and locations, with the fewest access levels the property can operate responsibly.
- Lost keys require a risk decision: identify the key’s access level and affected openings before choosing duplication, selective rekeying, or a broader change.
- Key and core custody, issuance records, return procedures, spares, and future expansion belong in the project scope.
Start here
Separate cylinders, cores, keyways, and key levels.
| Term | What it describes | What it does not prove |
|---|---|---|
| Rekey | Changes a cylinder or core so a new authorized operating key combination works and superseded keys no longer operate that cylinder | That the lock body, latch, door, or strike has been repaired or replaced |
| Keyway | The key and cylinder profile family that governs physical key compatibility and availability | The access hierarchy, cylinder format, or level of key control by itself |
| Master-key system | A planned hierarchy in which selected keys operate more than one keyed-different cylinder | Unlimited expansion or permission to issue high-level keys broadly |
| Conventional cylinder | A cylinder serviced in place or removed from the lock by a hardware-specific method | An interchangeable core |
| SFIC | Small format interchangeable core with a standardized core envelope used across compatible housings | Compatibility with LFIC, a particular keyway, or an existing control key |
| LFIC or FSIC | Large/full-size interchangeable core based on a manufacturer’s compatible housing and core family | A universal large-core format or compatibility across every manufacturer and product line |
| Control key | A specially keyed tool that removes and installs the matching interchangeable core through its control function | Authority to open every door or the same cuts and purpose as a master key |
Access design
Build the hierarchy around roles and doors.
The best key chart is usually the simplest one that supports real operations. Extra levels and exceptions increase administrative burden, key exposure, and future servicing complexity.
Change or operating key
This is the day-to-day key assigned to one cylinder or an authorized group of keyed-alike cylinders, such as a suite, utility group, or defined staff area.
Master key
A master key operates an authorized group of cylinders that also have their own change keys. The group should map to an operational role, not simply convenience.
Grand-master and higher levels
Higher-level keys can span multiple master-key groups. Their broader impact calls for tighter approval, issuance, storage, return, and lost-key response practices.
Control key
The control key activates the control function of matching interchangeable cores so an authorized person can remove or install them. Treat it as sensitive service custody even when it does not operate doors as a normal key.
Core formats
Choose SFIC, LFIC, or conventional cylinders from verified hardware and operations.
| Format | Service approach | Potential operational fit | Verify before selecting |
|---|---|---|---|
| Conventional cylinder | The cylinder is serviced in the lock or removed using the lock family’s supported process | Properties with stable doors, appropriate service access, and no need for rapid authorized core swaps | Lock family, cylinder type and length, cam or tailpiece, keyway, function, and service ownership |
| SFIC | A matching control key removes the small-format core from a compatible housing | Properties that value a common core envelope and controlled core inventory across compatible hardware | Housing, core length, keyway, pinning system, control key, master-key plan, and supplier authorization |
| LFIC / FSIC | A matching control key removes the manufacturer-family large/full-size core from compatible hardware | Properties already standardized on a supported large-core family or choosing one with a documented supply path | Manufacturer and product family, housing, keyway, control function, cylinder application, and future support |
Authorized workflow
A commercial rekey should leave an auditable handoff.
- Verify the requesting party’s authority for the property and the specific openings
- Identify the doors, locks, cylinders, core formats, keyways, and current key groups in scope
- Document lost, unreturned, contractor, tenant, and spare keys that influence the risk decision
- Define the desired operating-key and master-key relationships by role and location
- Confirm whether existing cylinders or cores can be supported, rekeyed, or must be replaced
- Reserve expansion where the system design and property growth require it
- Agree on key stamping, numbering, packaging, delivery, and the authorized recipient
- Test each changed cylinder with its assigned authorized keys and verify the lock and latch operation
- Transfer the opening schedule, issued-key record, core record, and custody responsibilities through a secure channel
- Store control keys, high-level keys, spare cores, and system records under named ownership
Risk decision
Respond to a lost key according to its reach and context.
Making another copy replaces convenience, not control. If a missing key still operates a cylinder, duplication does not remove that exposure. The property’s authorized decision-maker should assess the affected openings and choose an appropriately scoped rekey, core change, monitoring, or broader response.
| Question | Why it matters |
|---|---|
| Which exact key or key level is missing? | A suite key, building master, and control key expose different assets and response paths |
| Which openings does it operate or service? | The door list defines the actual scope rather than the number stamped on the key |
| Was it labeled with the property or door? | Identifiable keys can carry different recovery and misuse risk |
| Who last had custody and when? | Timing and custody inform incident response and record correction |
| Is there evidence of theft, termination, or targeted loss? | Context can increase urgency beyond a routine missing-key report |
| Can affected cores be changed in a controlled sequence? | Interchangeable cores may support a phased authorized swap when compatible inventory and records exist |
| Are electronic credentials also involved? | Mechanical keys and credentials need one coordinated access-removal process |
Ongoing operations
Key control is a process, not a phrase on a key blank.
Authorization
Name who may request keys, approve hierarchy changes, receive system records, and authorize emergency work. Keep the contact current when management changes.
Issuance and return
Record the key identifier, access level, recipient, approval, issue date, and return or disposition. High-level and control keys deserve especially narrow custody.
Duplication policy
A restricted distribution program can make unauthorized blanks or cutting more difficult, but property procedures still matter. Confirm the supplier, authorization file, and legal or contractual controls for the selected keyway.
Core and spare inventory
Label and store spare cores and cylinders by secure system references, not exposed door descriptions. Track where removed cores go and whether they remain keyed to an active hierarchy.
Records and succession
Keep the current opening schedule, hierarchy, key and core inventory, and service contacts available to the authorized property owner even when personnel or vendors change.
Site walk
Inventory enough detail to avoid locking the property into assumptions.
- Opening ID, location, door type, and business role
- Lockset, deadlatch, deadlock, exit device, padlock, cabinet, or other cylinder application
- Cylinder or core format, visible keyway information, and existing system identifiers
- Current operating, master, and control-key relationships known to authorized management
- Hardware condition, function, latch behavior, and door alignment
- Tenant, staff, janitorial, facilities, management, vendor, and emergency access needs
- Known lost keys, unreturned keys, duplication concerns, and former access paths
- Access-control credentials or smart locks that need coordinated role changes
- Future tenant turnover, phases, additions, and spare-capacity requirements
Decision path
Rekey the cylinder when the surrounding hardware remains the right fit.
| Path | Usually fits when | Confirm first |
|---|---|---|
| Rekey existing cylinder or core | The hardware is serviceable, the format and keyway remain supportable, and only authorized key operation needs to change | Cylinder condition, compatible components, hierarchy, keyway support, and door operation |
| Change or standardize interchangeable cores | The property needs controlled core swaps or is aligning compatible housings around a documented core program | Every housing, core format, keyway, control function, record, and spare requirement |
| Replace lock or cylinder hardware | The existing product is damaged, incompatible, unsupported, wrong for the door, or cannot provide the required function and key-control direction | Door preparation, function, strike, egress, accessibility, labels, access control, and system migration |
Common questions
Commercial rekey and core questions
Does rekeying replace the lock?
Usually no. Rekeying changes authorized key operation in a serviceable cylinder or core. The lock body, latch, trim, strike, door, and frame may remain unless their condition or the project direction calls for other work.
Is a control key the same as a master key?
No. A master key operates an authorized group of cylinders. A control key operates the control function used to remove and install matching interchangeable cores. Some systems may relate cuts in specific ways, but the roles remain distinct and must be documented.
Will any SFIC core fit any interchangeable-core lock?
No. SFIC refers to the small-format core envelope. The receiving housing, core configuration, keyway, control key, pinning system, and hierarchy still have to match. SFIC does not fit LFIC housings.
Can one key open every door in a commercial property?
A properly designed hierarchy can authorize a high-level key across selected groups, but broad access increases the impact of loss or misuse. The property should issue only the access each role needs and preserve system capacity for future changes.
Should every lost key trigger a full-building rekey?
Not automatically. Identify the missing key’s access level, affected openings, labeling, custody, and loss context. Then let the authorized property decision-maker choose a response proportionate to the actual exposure.
Sources and further reading
These references support the general technical guidance. The right answer for a specific opening still depends on the property and the authorities responsible for the project.
- Builders Hardware Manufacturers Association: ANSI/BHMA A156.28 Recommended Practices for Mechanical Keying Systems
- Builders Hardware Manufacturers Association: ANSI/BHMA A156.5 Cylinders and Input Devices for Locks
- Builders Hardware Manufacturers Association: ANSI/BHMA A156.30 High Security Cylinders overview
- Allegion: Commercial cylinder and interchangeable-core types
- Falcon / Allegion: Commercial key-control and SFIC keyway overview