A keyway is the shaped channel cut into the face of a lock cylinder that determines which key blanks can be inserted. The keyway profile — its specific pattern of cuts, shoulders, and warding — acts as the first mechanical barrier in a lock, physically preventing incompatible keys from entering the cylinder. Every residential deadbolt, commercial mortise lock, and padlock has a keyway, and the choice of keyway affects security level, master key compatibility, and key control.
Locksmiths encounter keyways on every job. Understanding keyway profiles, how they constrain bitting depth charts, and why keyway selection matters for key control is foundational knowledge that shapes everything from residential rekeying to 200-door commercial master key systems.
What a Keyway Does
The keyway serves two functions. First, it acts as a warding mechanism — the physical profile prevents incorrect keys from being inserted far enough to interact with the pins. Second, it defines the depth-and-space specifications for the bitting cuts that the key will carry.
Every keyway has a corresponding depth-and-space chart that specifies the allowable cut depths, the spacing between cuts, and the minimum adjacent cut (MACS) — the maximum difference between any two adjacent cuts that allows the key to enter and withdraw smoothly. These specifications define the universe of valid bitting combinations for that keyway.
A Schlage C keyway (SC1 or SC4) uses six cut positions with depths ranging from 0 to 9. A Kwikset KW1 uses five cut positions with its own depth chart. Yale's Y11 has a different profile again. The keyway is the foundation that all bitting decisions rest on.
Common Keyway Profiles
Residential locksmiths encounter a handful of keyway profiles on the vast majority of jobs:
- Schlage C (SC1/SC4) — The most common residential keyway in North America. Six pins, depths 0–9, MACS of 7. SC1 and SC4 are the standard Schlage profiles. Found in Schlage B-series deadbolts and knob sets.
- Kwikset (KW1/KW10) — Common in builder-grade hardware. Five pins, depths 1–7. Simpler warding than Schlage, and a known limitation in higher-security contexts.
- Yale (Y11) — Common in Yale residential cylinders. Five pins with Yale's proprietary depth chart. Less universal than Schlage or Kwikset.
- Corbin Russwin — Common in commercial mortise cylinders. Multiple keyway profiles (CG, CH, L4, and others) to allow keyway separation between departments in master key systems.
- Best SFIC — Small Format Interchangeable Core. Used in commercial buildings that want cylinders they can swap without tools, common in education and healthcare.
Commercial work introduces far more keyway variety. Manufacturers like Corbin Russwin, Sargent, Yale, and Medeco each offer dozens of profiles. This variety is intentional — keyway separation is a core master key system design tool.
Restricted vs. Unrestricted Keyways
Not all keyways are equal in terms of key control. The distinction between restricted and unrestricted keyways is critical for commercial security.
Unrestricted keyways (like Schlage SC1 or Kwikset KW1) have blanks available at any hardware store, locksmith supply house, or online retailer. Anyone can buy a blank and have a key cut — with or without authorization. Unrestricted keyways offer little protection against unauthorized duplication.
Restricted keyways are controlled through patent protection or proprietary manufacturing. Blanks are only sold to authorized dealers, and each sale is recorded. Restricted keyways are essential for high-security applications — schools, hospitals, government buildings, and any facility where key control must be enforced rather than trusted to goodwill.
Medeco, Mul-T-Lock, and Abloy are well-known restricted keyway systems. When a commercial client asks about key control, the keyway conversation usually starts with whether the current keyway is restricted. If it is not, any key in the system can be duplicated at any hardware store without the locksmith's or building owner's knowledge.
Keyways and Master Key Systems
Keyway selection has significant implications for master key system design. In a large master key system, keyway separation creates groups of cylinders that physically cannot share a key — even if the bitting were somehow compatible.
A university campus might use six different keyway profiles across its buildings. The science building uses one keyway; the administration building uses another. Even if a bitting combination would theoretically work in both keyways, the physical incompatibility of the key blank prevents cross-access. This is a security layer that no amount of pinning precision can replicate.
Warding is the mechanism that makes keyway separation work. Warding is the positive material inside the keyway channel — the bumps and shoulders that the key's warding cuts must clear for the key to enter. Each keyway has a unique warding pattern. Only the matching blank can navigate it.
For master key system designers, the number of available keyways in a manufacturer's line determines how many secure zones can be created without overlap.
How to Identify an Unknown Keyway
In the field, locksmiths often need to identify a keyway from a lock with no documentation:
- Visual comparison — Compare the cylinder's keyhole against reference cards or a keyway identification app. Most experienced locksmiths recognize common profiles by sight.
- Try known blanks — Insert candidate blanks gently to find one that fits without forcing. The correct blank slides in and out smoothly.
- Decode from a working key — The key blank's bow markings often identify the manufacturer and keyway family.
- Use a decoder — For cylinders with no working key, a decoder or plug follower can help identify the profile from the cylinder's internal geometry.
Keyway identification is the first step in any rekeying job. Order the wrong blank and the job stalls, regardless of how accurate your bitting calculation is.
Why Keyway Documentation Matters
Every cylinder record in a locksmith's files should include the keyway. Without it, a bitting specification is incomplete. The bitting tells you the cut depths; the keyway tells you which blank the bitting applies to. A bitting of 64253 on a SC1 keyway is a completely different physical key from the same bitting on a KW1.
In LockBench, the keyway is a first-class field in every cylinder record. When you create a pinning specification or bitting record, the keyway selection determines which depth-and-space chart is used for validation — ensuring every recorded bitting is mechanically valid before a key is ever cut.