Les Règles

When an opposition player is Knocked Down by this player as the result of a Block action (on its own or as part of a Blitz action), this player may immediately commit a free Foul action against the Knocked Down player.
To use this Skill, this player must be Standing after the block dice result has been selected and applied, and must occupy a square adjacent to the Knocked Down player.
After using this Skill, this player is Placed Prone and their activation ends immediately.

Q: The Pile Driver skill states that the player performing the Block action may then perform a 'free' Foul action against the Knocked Down player. Does this 'free' Foul action mean that it does not count towards the team's one Foul action per turn, or does it mean that the player can perform this action for free? (p.80)
A: This means that the player may perform this action for free. This Skill cannot be used if the team has already used their Foul action for that team turn, and if used will mean that another player cannot also make a Foul action during the same team turn.

Q: Does the free Foul action from Pile Driver happen before or after making the Armour roll (and potentially an Injury roll) for the player being Knocked Down? (p.80)
A: After, so long as the player is still on the pitch, of course!

Q: If my player with Animal Savagery trait lashes out against my own teammate and also has the Pile Driver skill, is my opponent able to make me perform a foul against my own teammate? (p.81)
A: No, they cannot force you to use the Pile Driver skill.

Q: Can a player that has been Rooted as per the Take Root trait use a skill such as Pile Driver or Wrestle in order to place themselves Prone and therefore no longer be Rooted? (p.87)
A: Yes.