The National Hockey League defines it in Rule 55 as "the act of using the stick in a manner that enables a player or goalkeeper to restrain an opponent."
The NHL covers hooking in Rule 55, which defines it as "the act of using the stick in a manner that enables a player or goalkeeper to restrain an opponent."
It goes on to specify that "when a player is checking another in such a way that there is only stick-to-stick contact, such action is not to be penalized as hooking."
The NHL groups hooking with other "Restraining fouls" such as holding, interference and tripping.
"[2] Both codes allow for hooking to be penalized with either a minor or major penalty; although hooking is usually a minor penalty, a major penalty can be imposed for injuring an opponent by hooking, and carries with it an automatic game misconduct.