Two linesmen are used to call offside, offside passes, icing, and handle all face-offs not occurring at center ice. Although they don't call penalties, they can recommend to the referee that a penalty be called.
One of the two officials primarily responsible for calling icing and offside violations. The linesmen also conduct most faceoffs, separate fighting players, and may inform the referee of fouls, but they cannot themselves call penalties.
Officials that travel the sidelines with a small flag in their hand to signal the referee when the ball goes out of bounds, or when they see an offside or any other violation of a rule. The final call is always up to the referee.
the referee's assistants. These officials wear black and white striped shirts, with no armbands. Their duties are the calling of offside, and icing calls, and where necessary assisting the referee to carry out his duties.