Nigel Owens has five years of professional refereeing experience
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.
This week Nigel Owens answers your questions.
If you would like to contribute a question, fill in the form on the right-hand side.
Answers will be posted every Tuesday after a Six Nations weekend.
Q: I coach an under-13s youth squad and recently have noticed a large discrepancy in the interpretation of the 'squeeze ball'.
When is it illegal to pass the ball between your legs and when is it a legitimate move?
Alex Evans, Swansea
A: At U18s level and below the squeeze ball - when a player places the ball between their legs after a tackle - is illegal and must be penalised.
At U19s and senior level the player may go to a squeeze ball position immediately as he goes to ground.
But the ball must become available and not held under his body or legs.
If the ball is not played immediately then it becomes a penalty offence.
Q: Could you please explain the penalty try law.
Scotland denied Wales a try-scoring opportunity in Cardiff
A penalty try will be awarded if a team in possession of the ball are denied a try-scoring opportunity because of foul play from the opposition.
So, for example, if the opposition deliberately:
- Knock on
- High tackle
- Kill the ball at a tackle or ruck
- Collapse or pop a scrum up
The referee will award a penalty try under the posts. The opposition can charge the conversion.
Q: I've seen professional players almost stamping on opposition when they are on the wrong side of a ruck.
Is it legal to "ruck" a player if he is on the incorrect side?
Josh Trimmer, London
A: Rucking is when a player on his feet and going forward uses his feet to move away a player who is lying over the ball.
He must try and make contact with the player's body on the floor and the ball at the same time.
Standing in the same place and stamping on a player when the ball is nowhere near is totally unacceptable and should be penalised.
Stamping is a red card offence.
Q: When a team is unable to field a sufficient number of front row players, non-contested scrums are enforced.
How do you decide when a player is sufficiently advanced to play in the front row?
Only specific players can take part in the front row for safety reasons
A: Each team must put FR (front row) next to the players' names on the teamsheet that can play in the front three.
It's the players and coaches who decide who can and can't play in the front row.
But they must inform the referee before kick-off.
Q: If the ball is kicked out of play and a member of the opposing team hits the ball back on field without their feet touching the ground, what is the verdict?
A: This is a hard one to explain.
If the ball is over the touchline and the player who is in the air is over the touchline, the ball is in touch no matter where it lands.
If the ball is in touch and the player is in the air, but in the field of play when he knocks the ball back into the field of play then it's play on, no matter if the player lands in touch after or that.
Phew! Hope that explains it.
Q: What is the rule on crossing?
I have seen several examples of what I consider crossing unnoticed or unpunished by the referee.
Sam Hayes, London
A: The laws state that if a player goes in front of a team-mate who is carrying the ball and interferes in any way with the opposition's defence, they will be penalised for offside or obstruction.
If the referee feels it didn't give the attacking team an advantage then play will continue.
Q: There seems to be increasing interference by the scrum-halves around the scrum after the ball has been put in.
Shouldn't this be penalised more as it must be a source of frustration?
Brent Tapscott, Oxfordshire
Scrum-halves often walk a tight line at scrums
A: You're right, it's becoming an issue.
The scrum-half feeding the ball now seems to slow up following the ball to the back of the scrum. This keeps the opposition scrum-half away from the ball so their number eight can pick up and gain yards.
This is a penalty offence for obstruction.
The opposition scrum-half can go past the feeding scrum-half if he wants, as long as he stays behind the ball.
However, some prefer to push and shove instead. But the referee should be able to manage the situation.
Q: When a team is awarded a penalty try, the kick for goal is given in front of the posts.
In the unlikely event that the kicker missed the target, would his team be awarded five points for the try or no points because the penalty was missed?
Colin Cooke, Munster
A: It's five points just like normal if you missed a conversion. I am refereeing Munster this Saturday against Glasgow, so let's hope this doesn't happen!
Q: How are referees instructed to use the video official in case of disputed tries? Has there been an unofficial line to use them less?
Television match officials are often called on for disputed decisions
Fourth officials are called TMOs, which stands for television match officials.
They are there to be used if the referee needs assistance in awarding a try or no try, foul play in goal, penalty kicks or drop goals.
It is up to the individual referee if and when he asks to use the TMO.
Q: If you kick the ball over the posts at a restart, do you get three points?
No I'm afraid you don't. You only get three points for a penalty kick at the posts or a drop goal.
Q: Do the opposition have to be back 10 metres when a free-kick is awarded? I think no but my mate doesn't agree.
Well, I'm afraid your mate is right. Hope you didn't put any money on it!