The lineout is a means of restarting play after the ball has gone into touch (off the field of play at the side). The lineout concentrates a selection of forwards in one place near to the touchline, so the backs have the rest of the width of the field in which to mount an attack. The key for the forwards is to win possession and distribute the ball effectively to the backline.
The forwards assemble in two lines, perpendicular to the touchline, one metre apart. The hooker throws the ball down the corridor between these two lines of players. Because the thrower’s team-mates know where the throw is likely to go, that team has an advantage in retaining possession. However, with speed of thought and movement, the opposition can contest for the ball and the lineout frequently results in a turnover of possession.
The player who successfully catches the ball can keep it and set up a maul, or can pass to the receiver (a player who stands next to the lineout to wait for such a pass) who then passes to the fly-half and on to the backline.
The assistant referee signals that the ball is in touch and which team has the throw in.
To allow players to catch high throws in the lineout, it is permissible for the catcher to be supported by team-mates while jumping to catch the ball.
Safety is a prime concern here, and any player who is off the ground must be supported until that player returns to the ground. A player may not be tackled while in the air, and holding, shoving or levering on an opponent are all offences punishable with a penalty kick.