Players stand on either side of the net, with one player throwing the ball up for their team mate to block.
Ball trajectory assessment and judging the correct time to react are essential to blocking effectively.
Ask players to block to specific areas, such as left, right or centre of court.
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.