Keyway

The keyway is the shaped slot in the front of a cylinder plug that accepts only key blanks with a matching profile. Look at any cylinder face-on: the keyway is the silhouette you’d see — a vertical slot with grooves and channels cut into its sides. A blank without those grooves can’t insert; a blank with the right grooves slides in.

The keyway shape is profile-specific. A Lockwood 570 cylinder accepts only Lockwood 570 (and compatible) blanks; an EVVA EPS cylinder accepts only EVVA EPS blanks. Mixing keyways is impossible by design.

Why keyways exist

The keyway is the mechanical layer of a profile’s identity. Combined with the bitting (the cut depths) and any side-bar requirements, the keyway determines whether a given key fits a given cylinder at all, before the depth math even matters.

Common warding patterns in a keyway include:

• Paracentric warding — the warding crosses the centerline of the keyway, so the key blade must have matching grooves on both faces. Standard for restricted profiles.
• Open keyway — minimal warding, easier blank manufacture, lower restriction. Schlage C.
• Stepped keyway — multiple warding grooves at different heights, more selective. EVVA EPS.

Master-keyed buildings and keyways

Within a single master key system, every cylinder must share a single keyway (or compatible keyways within a manufacturer’s family). You can’t mix Lockwood and Schlage cylinders in one MK system because the keyways are different — a key cut for one wouldn’t insert into the other regardless of the depth math.

This is why the first decision in any commercial MK design is the keyway. Everything downstream — TMK choice, MACS, allocation method, blank availability — is constrained by it.

Related

→ Restricted keyway — keyways with controlled blank distribution → Key blank — the uncut precursor to a key, profile-specific → Side bit — additional keyway features beyond standard pin-tumbler