Bitting

The bitting of a key is the sequence of cut depths from bow to tip, written as a string of numbers. A bitting of 4-2-6-3-5-1 describes a 6-pin key with cuts at depths 4, 2, 6, 3, 5, and 1 across positions 1 through 6.

Bitting is the canonical way to record a key’s specification — it’s what gets stored on the pinning card, what the code machine reads, and what the engine validates against MACS. Two keys with the same bitting (on the same profile) are functionally identical; cutting from a bitting is just a matter of feeding it into a code-machine app like InstaCode.

Reading a bitting

Conventionally:

• Position 1 is closest to the bow (where you grip the key).
• Position N is closest to the tip.
• Depths run from 0 (no cut, or shallowest) to 9 (deepest), inclusive.

A 5-pin Schlage C key written 52731 means: position 1 = depth 5, position 2 = depth 2, position 3 = depth 7, position 4 = depth 3, position 5 = depth 1.

Some manufacturers write bitting bow-to-tip; some tip-to-bow. The convention is per-profile and per-tradition. Keyzee normalises everything bow-to-tip in its exports for consistency.

Bitting and security

The bitting is, in some sense, the secret of the key. With it, the key can be reproduced from a blank in seconds. This is why high-security keys (UL437-listed, restricted-keyway, or with side-bar mechanisms) typically have other features that don’t get captured in the bitting alone — side-bit cuts, dimple positions, or angled rotations — so the bitting doesn’t tell you everything.

Related

→ MACS — the constraint every bitting must respect → TMK — whose bitting determines every other key’s → Change key — the leaf-level keys whose bittings derive from the TMK’s