Players stand on both sides of the net and all players have a ball in their hand. They are supposed to jump at the same time as the player opposite them and try to barge the opponent's ball out of their hands.
While jumping and pushing the ball, players develop balance and arm power as well as using the correct technique for putting their hands over the net as they would do when blocking.
Be sure that players always land at the same spot that they jumped off.
World Rugby has reportedly conceded Aaron Smith's disallowed try in the World Cup final should have stood.
"It is not only useful for staff who are experienced but a valuable tool for those subject staff who have to take teams."
The variety of sessions across sports - sometimes we steal session ideas from one sport and use them with another.