One player is the feeder with three other players standing at an equal distance in front of them.
The feeder begins by moving along the line in order, throwing a normal pass to each player for them to run onto and return as quickly as possible.
As the drill progresses the feeder can choose their player who they want to pass to - thus keeping all the receiving players on their toes.
They can also vary their passing technique. If the feeder passes to a player using a bounce pass for instance that player must pass back using the same passing technique.
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.