World Rugby (previously the IRB) regularly publishes the book of the laws of the game of rugby union.
Referees officiate each game of rugby using these laws which players are familiar with, to varying degrees of accuracy.
Players, particularly captains, who are well aware of the laws can have meaningful discussions with referee about decisions on the field but many players simply don't know the rules.
They can be forgiven, to a certain degree, for this ignorance.
The book has over 200 pages of laws and rules, which in itself is a challenge to understand.
But in addition, World Rugby also publishes annual law changes and variations.
These are often referred to as "experimental laws" and are not in the current law book. A few examples will suffice.
Under current law variations, at a scrum the halfback is now permitted to stand so that his shoulder (usually the left) is on the middle line, rather than stand so that the centre of his body is on the middle line.
If he did the latter the ball would go in along the centre line, like it used to have to do when most readers played the game.
Under the current variation the ball effectively goes straight under his front rowers' feet.
It must still be put in straight - ie on a line parallel to the middle line - rather than being fed in on an angle towards his hooker's feet.
This change has come about to make it easier for the team putting the ball in to hook the ball so that it doesn't just sit in the middle, where no-one can hook it because of the pressure exerted by the modern scrum.
Research has shown there have been fewer collapsed scrums since this variation was allowed and it will probably be written into law eventually.
At a lineout, the ball must now alight anywhere in the middle channel, which is the gap of a metre between the inside shoulders of opponents in the lineout.
That is quite a difference from alighting on the middle line as used to happen and may appear to be "not straight" to the naked eye, but that is the current ruling.
Another variation to the ball-in-touch situations has been exploited by a number of players, showing they are at least trying to keep up with current rulings.
Under the current law book, once a ball has crossed the touch line it is considered "out" unless a player standing in the field-of-play catches it before it hits the ground in touch.
If the ball has crossed the touchline, a player jumping to catch it or knock it back into the field of play has to land in the field of play, otherwise the ball is deemed to be "out."
A variation currently in force allows such a player to jump and knock the ball, or catch and throw it back, into the playing area, even if it has crossed the touch line and even if he lands in touch or touch-in-goal.
Touch judges should be aware of this change too, because they often have to rule if the referee is not close enough to make a judgement on the ball crossing touch.
Similarly, the law book currently says if a player catches the ball from a kick and has one foot on the touchline then the ball is in touch, whether it has crossed the line or not.
In this case the kicker's team were considered to have put the ball into touch, giving the catcher's team the lineout throw-in.
Under another current law variation in the above situation, if the ball has reached or crossed the touchline then the catcher's team would still get the throw-in to the lineout because the catcher is actually standing in touch.
But if the ball has not reached the touchline and the catcher has one foot on the line, his team are deemed to have put it out and the kicker's getting the lineout throw - another reason for touch judges to keep up with play.
The current changes relating to Dangerous Tackles have featured regularly in post-game debates this year and are likely to be written into the law book for next season.
There have been further experimental law variations in force in the Northern Hemisphere from August 1 which will come to our part of the world from January 1.
These same laws will be used when the All Blacks tour Great Britain later this year.
However, the ABs should not be too worried because most of them were being trialed here last season for the Mitre 10 Cup and Heartland Championship.
The most interesting one related to the tackle and ruck areas, and resulted in faster play and less clutter at the post-tackle situation.
The definition of a ruck was changed from one player from each team on their feet and over the ball on the ground, to just one player on his feet post tackle.
So, as soon as the tackle occurred and the tackled player and his tackler were on the ground (along with the ball), the next arriving player on his feet and entering straight from behind could put his hands on the ball and a ruck with off side liines is considered to have been formed
It all sounds pretty straight forward. Who would like to become a referee next season?