For scrum-halves, the offside line is the line of the ball fed into the scrum.

So that means they can't go past that line until the ball has been put into the scrum by the opposing number nine.

For all the other players, the offside line is an imaginary line drawn through the foot of the last player in the scrum.

No player apart from the eight forwards and scrum-halves are allowed in this area.

The opposing scrum-half has to wait until the ball is fully out of the scrum before making a tackle for the ball.

If they don't, then the referee will be on their case.

A penalty will be given at the place where the offence took place.