As part of our Six Nations coverage, we are giving you the chance to quiz two top Welsh referees about the laws of the game.
Nigel Owens answers your questions this week.
If you would like to contribute a question, fill in the form on the right-hand side.
28 Feb: Quiz the refs answers
Answers will be posted every Tuesday after a Six Nations weekend.
We start this week's answers with the poser set by Nigel Owens in the last forum. He asked: What are the four ways of scoring a try without the ball crossing the line?
For those of you tearing out your hair in frustration, they are:
The last one's a bit sneaky but there you go!
Q: Can you tell me how the one-metre gap law at the line-out is interpreted?
Nick Buttle, Kent
The one-metre gap must be adhered to until the ball is thrown in.
The problem is when players swap positions before the ball is thrown in, as they are allowed to do, and when both sides jump for the ball.
But as long as the team that wins the ball does so fairly, then referees will allow play to go on.
Q: Is it true that if you cross the opposition's tryline with the ball in your hands and you touch the referee it is a try?
Alex, Northern Ireland
The answer is 'no', unless the referee has stopped the player grounding the ball. If this happens then a try should be awarded.
If you gain advantage by scoring in a better place because the ref was in the way, then the touchdown or try should be where you made contact with him.
Q: After blowing for an infringement, can a referee change his mind, without any influence from touch judges or players?
M Jackson, Cornwall
No. However, it is a very difficult situation if a referee knows they have given the wrong decision.
Q: When a player marks a catch in his own 22-metre line, do they have to kick it away or is it OK to tap it to himself and then pass? When can the opposition run towards that player?
Laurence Hogan, Wellington NZ
The player can tap the ball and run or tap it and pass to his team-mates.
The opposition can charge once the player has tapped it or as they start the run-up to kick, as long as they are 10 metres back.
Q: When a scrum wheels more than 90 degrees the referee will reset it.
Sometimes the feed goes to the side that had the put in at the first scrum and sometimes it goes to the other side. What is the law governing this?
Bob Sterritt, East Grinstead
The law says the side who was not in possession of the ball when the scrum wheeled 90 degrees should have the put in at the next scrum.
However, at under-19 level and below it is the same team that has the put in and the scrum cannot turn more than 45 degrees.
Q: Can the hooker lift the person at the front of the line at the opposition's throw in if they are standing in the five-metre channel?
Ben, Cardiff
Yes they can as long as they lift from the channel or on the five-metre line.
The hooker cannot enter the line-out. If they do, it immediately becomes an offence as their team would have more numbers in the line-out than the team throwing in.
A free-kick is awarded for this offence.
Q: Is there a maximum number of substitutes that any one team can make during a game?
And if a front row specialist is taken off for tactical reasons, can he be brought back on if injury means a front row specialist is needed?
Craig Mathie, Bournemouth
You can use all seven substitutes if required. A front row player who has been taken off for tactical reasons can come back on if a front row player becomes injured.
However, the player they replace is out of the game for good. They also must be injured for the substitute to return to the front row.
Q: Just after a line-out has been thrown I sometimes see the ref holding his arm up vertically with an open palm. There is no whistle and play continues.
What is the ref doing? Is he signally to the fourth official? If so what is he saying?
Matt, Cambridge
He is waving to his mother who is watching at home - only joking!
He is telling the players not in the line-out that it has yet to finish. They must stay back at least 10m until it finally does end.
So the fly-half or anyone not in the line-out must be back 10m or on their goal-line, whichever is nearer until the line-out ends.
The referee will then drop his arm when the line-out is over and the other players can join in.
As usual, a little poser - How many different ways can a line-out end? And don't say when the ref drops his hand!
Q: Can you please explain the truck and trailer situation?
Thomas, London
A difficult one to explain. When a maul is moving forward and the ball is at the back with the last player, in order for it to be legal that player must be fully bound onto the maul with at least one full arm.
If that player detaches or holds on to the back of the maul with just his hand then it is obstruction.
Some referees have called this move "truck and trailer". Phew! Hope that explains it.
Q: When a player hits the deck, how long do they have to release before the referee blows for holding on?
Johnny Bowen, Brecon, Wales
The tackled player must release the ball immediately, the player on his feet who wants to play that ball has the priority every time.
But if no-one is there on their feet to play that ball then the referee may allow them a second longer to place or release it.
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