A ruck is formed when at least one player from each team are in contact, on their feet and over the ball which is on the ground. Players involved in all stages of the ruck must have their heads and shoulders no lower than their hips.

What happens in a ruck?

The ruck. A ruck is formed if the ball is on the ground and one or more players from each team who are on their feet close around it. Players must not handle the ball in the ruck, and must use their feet to move the ball or drive over it so that it emerges at the team's hindmost foot, at which point it can be picked up ...

When can you pick up the ball in a ruck?

As long as a ruck is formed, no players can pick up the ball until the ball is exposed again, usually because one team has pushed the other team back far enough that they have won the ball. A ruck can be formed over any ball on the ground, but is most common after a tackle.