If a unit wins the combat and its formation already extends to the enemy's flanks then models may be moved from the rear ranks round the sides of the enemy unit. These extra models are described as lapping round. You may move up to two models around each flank, assuming that there is room and chat the flank is not blocked by anoilier unit, buildings, or terrain. Once models have covered the enemy's flanks, further models may be lapped around the rear should they win a further turn. In this way, it is possible to extend your line and surround an enemy unit completely.
If a unit which is lapping around is successfully charged by fresh enemies that can reach them, the lapping models will immediately return to the rear rank of their formation. The chargers will be moved into contact with the reformed unit if their charge reach is sufficient. If they can no longer reach the charged unit because models in it have been moved to the rear ranks, the charge counts as having failed.