Blue players pass the ball around the grid, always throwing the ball in front of the player so that they have to meet the ball.
As the blue players run out to meet the pass green 1 and 2 must also run out to contest and defend the ball.
To begin with defenders are fairly passive, as the drill progresses though you can increase their role.
To make the drill more live blue players can choose which direction to pass the ball around the grid and green players are allowed to try and win the ball - if they successfully tackle the ball they swap places with the outside player.
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.