A line-out is the means by which, in rugby union, the ball is put back into play after it has gone into touch. It is the equivalent of the throw-in in association football. Rugby league does not have line-outs. Instead, a scrum takes place 20 metres infield from the spot where a line-out would have taken place in rugby union.
When a player puts the ball into touch (that is, out of the field of play) the opposing team is awarded a line-out. An exception is that if the ball is kicked into touch from a penalty kick, the team that was awarded the penalty throws in to the resulting line-out.
Where the line-out is taken depends on the manner in which the ball was played into touch. If it is kicked directly into touch, without first landing in the field-of-play or touching the referee or an opponent who is not in touch, the line-out is formed in line with the spot from where it was kicked, with two exceptions: if the kick was a penalty kick or if the kicker had at least one foot on or behind his own 22-metre line, the line-out is formed at the spot where the ball crossed the touch-line. In all other cases, the line-out is formed at the spot where the ball crossed the touch-line, except that if this spot is within 5 metres of the goal-line, the line-out is formed on the 5-metre line. A line-out is also awarded if a player in possession of the ball, crosses or touches the touchline whilst still in possession of the ball.
A line-out is formed with a minimum of two players from each side; the maximum number is determined by the team throwing in and their opponents must not have more players in the line-out (though they can have fewer). The players forming the line-out must stand at least 5 metres, but not more than 15 metres, from the touch-line, in two parallel lines, each team's players standing at least half a metre on their side of the "line of touch" (an imaginary line extending the full width of the pitch, at right angles to the touch-line at the point where the line-out is formed), so that there is a gap of at least one metre between the opposing lines.
A player from the throwing team, usually (but not always) the , throws the ball in. He stands with both feet outside the field-of-play and must throw the ball straight, along the gap between the teams, without feinting or dummying the throw. The thrower may throw the ball as high and as far as he wishes and players forming part of the line-out are allowed to jump up and catch the ball. Players who do not themselves jump for the ball may support a jumper from their team, but are not allowed to lift the jumper or otherwise support him before he has left the ground, provisions that are rarely enforced in practice.
A player in the line-out will attempt either to catch the ball or to knock it back to a "receiver", a player of his own side, often the but sometimes another forward, who is standing close to the line-out on his own side in a position to receive such a ball. Each team may have, at most, one receiver at a line-out. If the line-out player catches the ball he may hold on to it and allow a maul to form, or pass it to another player.
Players not forming part of the line-out, or acting as receiver, must stay at least ten metres from the line of touch until the line-out is over, except that if the line-out is formed within 10 metres of their goal-line, they need only retreat behind the goal-line. A line-out ends when the ball, or a player carrying it, leaves the line-out, or, if a or maul is formed at the line-out, when all the feet of all the players forming the ruck or maul move beyond the line of touch.
Teams usually employ a line-out code, to ensure that all players on that team know what is planned, who the ball will be thrown to, what that player will do with it, and what follow-up ploy is intended. One player from the throwing team is usually designated to shout the code, and it is particularly important that the thrower should know what the code is, so that he can execute the throw as intended.
Players must not interfere with the opposition during the line-out. In particular, they must not interfere with or tackle a jumper while his feet are off the ground, or interfere with players supporting him; such actions are deemed to be dangerous play and will be penalised with a penalty kick. Players in the line-out must not close the gap or enter the gap, except in the act of jumping for the ball, nor may they jump or support a jumper before the ball is thrown; such actions are penalised with a free-kick. Penalty kicks and free kicks are awarded 15 metres infield from the touch-line.
If the ball is thrown beyond the 15-metre line, a player from the throwing team who is not taking part in the line-out may run forward to take the ball. If he does so, an opponent may also run forward to contest possession. Players who are taking part in the line-out may move beyond the 15-metre line as soon as the ball leaves the thrower's hands. If, however, a player runs forward or infield and the ball is not thrown beyond the 15-metre line, that player is off-side. The line-out ends when the ball crosses the 15-metre line.
Players from the side not throwing may jump to compete for the ball, though they must be careful not to attract a penalty for interfering with an opposing jumper. Alternative, they may choose not to contest the line-out but to drive onto the catcher as soon as he returns to the ground. Often, when a team is awarded a line-out close to their opponent's goal-line, they will attempt to form a maul around the catcher and drive over the goal-line to score a try. In such cases, the defending team will often seek to disrupt this tactic by driving in on the catcher, taking him to ground immediately, before a maul can form.
The IRB is currently evaluating a number of "experimental law variations" (ELVs, also known as the Stellenbosch Laws because they were first trialled at the University of Stellenbosch, in South Africa). The proposals have important implications for the line-out:
As part of the IRB's continuing process of evaluating the proposed changes, SANZAR recently agreed to implement some of the ELVs during the 2008 Super 14 and Tri Nations series, but among the changes that they decided not to implement were those affecting numbers at the line-out.