Players lay down on the floor and swing on their chest, raising their arms and legs alternately.
This drill is great for preparing players for sliding on their chest when diving and digging.
If players find it difficult to begin with, it may be helpful to pull their legs upwards so they are only having to work on raising their arms.
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.