The purpose of the scrum is to restart play quickly, safely and fairly, after a minor infringement or a stoppage.

A scrum is formed in the field of play when eight players from each team, bound together in three rows for each team, close up with their opponents so that the heads of the front rows are interlocked. This creates a tunnel into which a scrum half throws in the ball so that front row players can compete for possession by hooking the ball with either of their feet.

The middle line of a scrum must not be within 5 metres of the goal line. A scrum cannot take place within 5 metres of a touchline.

The tunnel is the space between the two front rows.

The player of either team who throws the ball into the scrum is the scrum half.
As soon as the front rows have come together, the scrum half must throw in the ball without delay. The scrum half must throw in the ball when told to do so by the referee. The scrum half must throw in the ball from the side of the scrum first chosen.
The scrum half must throw in the ball straight along the middle line.
The scrum half must not pretend to throw the ball.

The middle line is an imaginary line on the ground in the tunnel beneath the line where the shoulders of the two front rows meet.

The middle player in each front row is the hooker.

The players on either side of the hooker are the props. The left side props are the loose head props. The right side props are the tight head props.

The two players in the second row who push on the props and the hooker are the locks.

The outside players who bind onto the second or third row are the flankers.
A flanker may bind onto the scrum at any angle, provided the flanker is properly bound. The flanker must not widen that angle and so
obstruct the opposing scrum half moving forward.

The player in the third row who usually pushes on both locks is the No.8.
Alternatively, the No. 8 may push on a lock and a flanker.

BINDING IN THE SCRUM

When a player binds on a team-mate that player must use the whole arm from hand to shoulder to grasp the team-mate’s body at or below the level of the armpit. Placing only a hand on another player is not satisfactory binding.

WHEN THE SCRUM BEGINS and ENDS

Play in the scrum begins when the ball leaves the hands of the scrum half.

When the ball comes out of the scrum in any direction except the
tunnel, the scrum ends.

A scrum cannot take place in the in-goal. When the ball in a scrum is on or over the goal line, the scrum ends and an attacker or a defender may legally ground the ball for a try or a touch down.