When skirmishing units are engaged in hand-to-hand combat, it is possible that some models will be fighting whilst others are left out of the combat. In this case any models not fighting the enemy are allowed to move in their movement phase and shoot at suitable targets in their shooting phase.
Models not already fighting must move into the combat in subsequent turns if they can possibly do so. Models are moved as part of ordinary movement, no charge is declared, and they do not count as charging.