There are also a few variations at the Under-19 level of rugby union.
LAW 3 - NUMBER OF PLAYERS - THE TEAM
(5) (d) If a team nominates 22 players, it must have at least six players who can play in the front row in order that there is replacement cover for the loosehead prop, hooker and tighthead prop.
(5) (e) If a team nominates more than 22 players it must have at least six players who can play in the front row in order that there is replacement cover for the loose-headprop, hooker and tighthead prop. There must also be three players who can play in lock position.
(13) (b) A player who has been substituted may replace an injured player.
LAW 5 - TIME
Each half of an Under-19 match lasts 35 minutes playing time. Play in a match lasts no longer than 70 minutes. After a total of 70 minutes playing time, the referee must not allow extra time to be played in the case of a drawn match in a knock-out competition.
LAW 20 - SCRUM
(1) (f) In an 8 person scrum the formation must be 3-4-1, with the single player (normally the Number 8) shoving on the two locks. The locks must pack with their heads on either side of the hooker.
Exception: A team must have fewer than eight players in its scrum when either the team cannot field a complete team, or a player is sent off for Foul Play, or a player leaves the field because of injury.
Even allowing for this exception, each team must always have at least five players in a scrum.
If a team is incomplete, the scrum formation must be as follows:
If a team is without one player, then both teams must use a 3-4 formation (i.e. no No.8).
If a team is without two players, then both teams must use a 3-2-1 formation (i.e. no flankers).
If a team is without three players, then both teams must use a 3-2 formation (i.e. only front rows and locks).
When a normal scrum takes place, the players in the three front-row positions and the two lock positions must have been suitably trained for these positions.
If a team cannot field such suitably trained players because:
either they are not available, or
a player in one of those five positions is injured or has been sent off for Foul Play and no suitably trained replacement is available, then the referee must order uncontested scrums.
In an uncontested scrum, the teams do not compete for the ball. The team putting in the ball must win it. Neither team is allowed to push the other team away from the mark.
Front rows coming together. Each prop touches the opponent’s upper arm and then pause before the front rows meet. The sequence should be: crouch, touch, pause, engage.
No wheeling. A team must not intentionally wheel a scrum.
Penalty: Penalty Kick
If a wheel reaches 45 degrees, the referee must stop play. If the wheel is unintentional, the referee orders another scrum at the place where the scrum is stopped.
Maximum 1.5 metres push. A team in a scrum must not push the scrum more than 1.5 metres towards their opponents’ goal-line.
Ball must be released from scrum. A player must not intentionally keep the ball in the scrum once the player’s team has heeled the ball and controls it at the base of the scrum.