G41

During each CROSSING, a ROBOT may not cause more than one (1) BOULDER to move from the NEUTRAL ZONE into the opponent’s COURTYARD.

Violation: TECH FOUL per additional BOULDER

For example, if a Red ROBOT is CROSSING the Blue OUTER WORKS and a Blue ROBOT causes a BOULDER to bounce off of the Red ROBOT and through the OUTER WORKS, there is no violation of this rule as the action was caused by the Blue ROBOT.