OF ALL the phases of play during an 80 minute game of rugby - 70 for schoolboys - the one that is perhaps the most difficult for players and spectators to understand, but also the most common, is the tackle.
For those of us old enough to remember the days when rucking ruled the roost, there was the "standing" tackle where the ball carrier had to do something with the ball while others struggled to gain possession of it.
If the ball carrier went to ground the feet would start going and the ball (and sometimes the player) would emerge quickly out the back of the ruck and off out to the backs it went.
So what has changed since those good old days? What is a "tackle" now and what are the participants allowed, or not allowed, to do?
A "tackle" only happens now when the ball carrier is brought to the ground in the field of play, including being on one or both knees, while being held by an opponent at that time. A tackle cannot occur in the in-goal area.
Opposition players who bring the ball carrier to ground, then go to ground themselves, are known as "tacklers" and they have to comply with certain conditions.
Players who bring the ball carrier to ground but remain on their feet are not "tacklers" and have a different set of obligations.
Such players are sometimes referred to as "tackle assists" but this is not a term in the rule book.
The tackled player on the ground must immediately do one of two things - release the ball or pass the ball. He (or she) must also either get up or move away from the ball. Releasing the ball can include placing it on the ground in any direction, except forwards, and this may include pushing it along the ground. Tackled players often push the ball back between their legs, but it needs to be clearly seen by other players and not covered by the player's body.
If the player is tackled near the goal line, they may reach out and score a try, while they may also score if momentum carries them over.
The tricky aspect of the law relates to the players who bring the ball carrier to ground.
"Tacklers" - those who end up on the ground beside the ball carrier - must immediately release them and get up, or move away from the player.
Once on their feet, such "tacklers" may then attempt to play the ball from any direction.
If the opposition player has remained on his feet at a tackle, they must first release the ball and the tackled player, then they can play the ball, provided they are standing behind the ball carrier - facing their opponent's goal line.
They cannot play the ball from any direction like a tackler who went to ground can - first they must turn and come at the ball from directly behind. Arriving players may also attempt to play the ball, provided they also come from directly behind - the so-called "through the gate".
The tackle is a dynamic part of the modern game of rugby.
Things happen fast. Referees have a very short time to observe what the different players are doing at a tackle and who is or isn't complying with the requirements of the law.