The poacher
I like to call a defending player standing over the ball at the ruck the "poacher", because he's looking to poach or steal the ball.
When cleaning him out at the ruck your players have three options, depending on the stance of, and the threat level posed by, the poacher.
1. The poacher stands nearly upright over the ball
Threat level: low to moderate
The first cleaning out player to the ruck should aim to hit with their shoulder into and through the midriff of the poacher. The player should bind on tight as he drives through.
This player must drive straight through, without twisting to the side after contact, otherwise the poacher might spin or step out of the clean out.
Alternatively the first cleaning out player may simply secure the ball, leaving the poacher for a second player to clean out.
2. The poacher bends over the ball with hips in line with the shoulders
Threat level: medium to high
The first cleaning out player should aim to hit with their shoulder just below the poacher's shoulders, using explosive leg movements. Ideally, as they approach the player's shoulders and hips should be lower than the poacher's.
Lighter or off balance poachers may be driven straight off the ball. However, heavier and stronger poachers may need to be removed using the cross over "grab and twist" method, especially if the player can't get underneath them initially.
keeping the ball where it is, by getting their body on or over it.
3. The poacher illegally covers the ball with the hips above the shoulders
Threat level: maximum
The first cleaning out player should aim to hit with their shoulder between the poacher's shoulders and hips. Contact must be safe but strong enough to rock the opponent back onto his heels, by driving his hips backwards.
The player immediately should wrap his arms tight around the defender's hips (not his chest) and remain in tight contact throughout.
He should roll the defender outwards, away and off the ball, looking to end up on top of the poacher. The player should use their outside knee to twist in on the poacher's arm as they roll.
All this needs to be done in one fluid movement.
Support players must secure the ball as it is uncovered or freed.