There are often times in a game of rugby when players are unsure of what they can do with the ball when it is lying on the ground, especially after a tackle.
Knowledge is all powerful and players who do know the rules can often use them to advantage in critical stages of a match.
Law 14 refers to a situation where the ball is on the ground but no tackle has occurred.
This could be when the ball is available and a player goes to ground to gather it, or when a player in possession goes to ground without being tackled.
In these situations the player on the ground with the ball must immediately do one of three things - get up with it, pass it, or release it on the ground.
They should also get up and move away at once but, obviously, most are reluctant to leave when an opponent is about to gain possession.
If the ball is on the ground, no player may lie on it to prevent others gaining possession, nor can they tackle, or attempt to tackle, an opponent while still on the ground themselves.
Arriving players on their feet must not intentionally fall on or over a grounded player who is holding the ball, or over players on the ground with the ball between them.
This situation often occurs after the ball is kicked down field and there is only one defender to gather it.
Such defenders usually go to ground in the act of gathering the ball because they know they cannot be legally tackled until they get back to their feet.
Smart players on the ground can often buy time to allow team mates to catch up and form a ruck - while unknowlegable attackers often err by falling over the defender on the ground, thus preventing him from getting back to his feet.
Effectively, players on the ground are out of the game until they get back to their feet, but other players must attempt to stay on their feet if the ball is on the ground.
One other important consideration is that players may not dive on the ball as it is emerging from a scrum or ruck, nor may a player who gains the ball at or after a tackle go to ground with it.
I regret to say that we often see players on TV getting away with all three of these offences, but if you remember the cardinal rule - being on your feet to play the ball - this should not be allowed to happen.
If you can dive on the ball in these situations then you can just as easily bend down and pick it up - the game is meant to be for players on their feet.
Law 15 refers specifically to the tackle, what it is, and what players can and cannot do at a tackle.
For a tackle to occur, the ball carrier must be held by one or more opponents and brought to the ground.
Opponents in the tackle who also go to ground are known as "tacklers" and have certain rights that players who make a tackle but stay on their feet don't have.
At a tackle, the referee first looks at the actions of the tacklers, if there are any.
Tacklers must release the grounded ball carrier and get back to their feet before attempting to play the ball, which they can do from any direction, provided a ruck or maul has not begun.
This is an important distinction because all other players need to come "through the gate", which means they must come from behind the ball and be facing their opponent's goal line when they attempt to play the ball.
The referee then turns his attention to the actions of the tackled player, who must immediately make the ball available so play can continue.
He can do this by passing or releasing, including placing it in any direction, or pushing it backwards along the ground, not forwards.
I bet a lot of people are thinking, "how quickly is immediately"?
That is a very good question, but the answer depends a little on the situation.
If the tackled player is immediately surrounded by team mates who have been well-coached to step over both them and the grounded tacklers, so there is unlikely to be a contest for the ball, then referees generally allow a few seconds for the ball to be played by the tackled player.
However, if the tackle is of the dominant variety where the tackler, perhaps supported by a team mate or two, drives the ball carrier backwards and into the ground then they are in a position to play the ball the moment the ball carrier hits the ground.
That tackled player must play or release the ball straight away.
These players, who have brought him to the ground, are not tacklers and must release the tackled player and the ball before they can attempt to play it.
Other opponents, who are on their feet and come thought the gate, can also play the ball immediately - these players are sometimes referred to as the "jackal."
In this situation there is likely to be a contest for the ball, so the tackled player would be expected to release or play the ball straight away.
The other key picture - referees use "pictures" of what they expect to see at each phase of play - which the referee is looking for is players staying on their feet at the tackle.
Opponents of the tackled player must support their own body weight and cannot put their hands on the ground or on grounded players while trying to gain possession.
At a tackle, there are no offside lines, as the Italians so brilliantly showed recently.
However, very few tackles remain as such for long and usually move into a ruck or maul, where the offside line is the hindmost foot of players in each team in the ruck or maul.