N

NCK
symbol for `no change key,` primarily used in hardware schedules

NMK
a keying symbol which means `not master keyed` and is suffixed in parentheses to the regular key symbol. It indicates that the cylinder is not to be operated by the master key(s) specified in the regular key symbol; e.g., AB6(NMK).

non key retaining
adj. of or pertaining to a lock whose key can be removed in both the locked and unlocked positions