Rugby union is a contact sport that consists of two teams of fifteen players. The objective is to obtain more points than the opposition through scoring tries or kicking goals over eighty minutes of playing time. The play is started with one team drop-kicking the ball from the halfway line towards the opposition. The rugby ball can be moved up the field by either carrying it or kicking it. However, when passing the ball it can only be thrown laterally or backward. The opposition can stop players moving up the field by tackling them. Only players carrying the ball can be tackled and once a tackle is completed the opposition can compete for the ball. Play continues until a try is scored, the ball crosses the side line or dead-ball line, or an infringement occurs. After a team scores points, the non-scoring team restarts the game at the halfway with a drop kick toward the opposition. The team with the most points at the end wins the game.