Slightly old-fashioned term for what is usually today called a "Billy Club" or (UK) an officer's baton, a rodlike piece of
wood, usually painted
black, worn by police to strike or subdue suspects.
In the USA many registered, private security guards who are not licensed to
carry firearms may carry a Night Stick.
Certain phallic implications are almost inevitable.
.
.
In the 1940s, practically every
American beat patrolman was equipped with a .
38 revolver and a black Night Stick.