After all, not many referees have played in the front row and some front row players dislike being told what to do by a 60 or 70 kg twenty-three or twenty-four year old.
Once on the field the first scrum of the game is the test of how well the referee has set up the process for scrums during the game.
The referee will make a mark in the ground and players have 30 seconds to be ready for the scrum to set.
Normally, there will be eight players in each team in the scrum, plus the two half backs.
If a team is missing a forward as a result of a player being yellow or red carded then in adult rugby they may have only seven players in their scrum against the eight of the opposition.
In schoolboy rugby and Under 19 grades and below numbers must always be matched.
The engagement process of a scrum consists of three calls from the referee.
Once all the players are bound together and in a stationary position, the referee calls "crouch" and the front row players will do this, keeping their head and shoulders above their hips. At this point they should also be in a position of ear-on-ear.
On the "bind" call the props bind onto their opponent with the loosehead's arm inside that of the tighthead.
In all games I have refereed this season front row players have got this back to front in the first scrum, which is a little worrying as it shows a distinct lack of front-row player training at senior level.
The players should still be in the ear-on-ear position but often in levels below premier rugby here, the front rows will actually engage the shoulders at this point.
While this is not strictly desirable (or even legal) referees will often permit this if the scrum stays stable and no-one gains an advantage from the early engagement.
For the local premier competition and levels above such as Super Rugby there should still be a gap between the shoulders of opposing front rows until the referee calls "set" when the so-called hit between the front row occurs.
At this point players should be holding their weight steady until the ball goes in, when they can begin pushing forwards.
Referees look for stability before the half back puts the ball in but this sometimes doesn't happen because one team is already pushing over the mark in an effort to get in a better position to hook the ball.
Once the scrum is stable the halfback should put the ball in quickly and straight.
There are five other requirements of the halfback putting the ball in but if his forwards are under pressure he might be reluctant to do so and hold onto the ball in the hope the referee will free-kick the opponents for an early shove.
If not, he can be free-kicked for delaying the put-in – the referee has to decide what the cause and effect is here.
The scrum actually begins when the ball leaves the hands of the player putting it into the scrum. Front row players from each team may use either foot (but not both at the same time) to win possession of the ball.
Players in the scrum must push straight and square and not deliberately wheel the scrum.
If the scrum does wheel more than 90 degrees it will be re-set, with the team who first put the ball in doing so again.
Other reasons for a referee re-setting a scrum include if the ball comes out at either end of the tunnel, if the ball is unintentionally kicked out of the tunnel, if the scrum collapses before it has ended, or if neither team wins the ball.
Referees dislike re-set scrums so if the scrum collapses and the ball is available to play most wave play on.
Dangerous actions in the scrum include intentionally lifting an opponent off his feet or forcing him upwards out of the scrum, or intentionally collapsing a scrum and these actions should be penalised immediately.
Half backs have their own designated off-side lines at a scrum.
The half back not putting the ball in must stay close to the scrum and keep both feet behind the ball.
Or he can retire to the hindmost foot of players in his team in the scrum, or he can go back another five metres to the backs' offside line.
All the other backs have an offside line which is at least five metres behind the feet of the hindmost player in their team.
The scrum ends when the ball has left the scrum, or when a player at the back picks up the ball, or when the referee blows the whistle for an infringement, and there can be a lot of those.
The other way a scrum can end is when the ball crosses the goal-line, at which point any player can dive on it, usually the number eight of the attacking scrum.
