Characters are tempting targets for the marksmen in the enemy army – one well-placed volley and a powerful foe can perhaps be brought down before they have the chance to wreak ruin. However, picking out a lone character in the midst of a clamorous battle is harder than you might think. At a distance it can be hard to tell officers and common soldiers apart, particularly when units are advancing, marching and charging all around you, so we give lone characters a little protection to represent this.
If a lone character is hit by a shooting attack of any kind (including shots fired using ballistic skill, templates and so on) a "Look Out Sir!" roll can be attempted, provided there is a friendly unit consisting of five or more rank and file models of the character's troop type within 3". Roll a D6. On a roll of 4+, the character has been successfully forewarned or otherwise preserved from harm by their nearby allies the hit is transferred to a model in the friendly unit (if there is more than one eligible unit within 3", the controlling player can decide which made the honourable sacrifice). Otherwise, the hit is resolved against the character as normal.
You'll notice that the there is a chance of this "Look Out, Sir!" and it does not work automatically like the one discussed previously. This is only fitting as it's far harder to warn a friend from a distance than if they stood a few paces away.