The red line in hockey is a line on the rink that runs directly through center ice. The red line divides the rink into two equal halves.
The red line is important in hockey because it is used by referees to call an icing infraction.
If a player has the puck on one side of the red line and hits it to the other side of the red line and it goes to the goal line without being touched by a player on the opposing team, icing will be called.
The red line is also an important part of hockey strategy. Coaches use the red line as a benchmark for formations, plays, and more.