the far blue line without someone on your team touching it. its to stop people from just shooting it down the ice all them time. There are some exceptions, which is what makes the rule hard to understand. If the team who shoots the puck gets to it first, no icing. If a player should have gotten the puck but wasn't trying, the ref can also waive off icing. If you are down a man on the power play, you can't ice the puck.