If the ball is held up off the ground, once more than any two
players have bound together a maul is formed. If the ball has gone to
ground, then the group of bound players is called a ruck. The very
important principle of rucks and mauls is that once they are set, two
imaginary offsides lines become present at the back of each team's
rucking/mauling players extending from touchline to touchline. Any
player running into the zone who is not joining the ruck or maul, from
behind this line, before the ball leaves is considered offside and a
penalty can be awarded to the other team.
A simple representation of this concept is as follows:
