Defence (defense in the United States) in ice hockey is a player position whose primary responsibility is to prevent the opposing team from scoring. They are often referred to as defencemen, D, D-men or blueliners (the latter a reference to the blue line in ice hockey which represents the boundary of the offensive zone; defencemen generally position themselves along the line to keep the puck in the zone). They were once called cover-point. A good defenceman is both strong in defensive and offensive play and for defenceman pairing also need to be good at defending and attacking.