Rob

Here are IRB Law variations for Under 19 scrums:

20.1 (f) In an 8 person scrum the formation must be 3-4-1, with the single player (normally the Number 8) shoving on the 2 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.

You can find these and all laws for the game at irblaws.com

I hope this helps

Simon