Players throw the ball into the numbered areas. If the ball hits the floor directly, the team gets the number of points allocated to that area of the grid.
Two players on the other team however have got a big sack and try to catch the ball before it hits the ground.
If the catching team stops the ball from hitting the floor they get the number of points that would have been allocated to the throwing team.
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.