FAQ: Cover

When is a unit in cover? The answer is only when it's very obvious that the unit is in or behind terrain which would shelter it from enemy fire. This means that the line of fire must cross the terrain for it to be effective as cover, or the target must be positioned in an area of terrain which gives it cover. Whether a unit benefits from cover only if it's fully behind or in it, or if not how much of the model needs to covered is left to player choice - applying a hard and fast rule is inappropriate.

How we play the cover basically depends on just how much terrain is on the battlefield - if there's lots of cover we only count units in cover if they are completely in or behind it. If terrain is sparse we're more generous and count units as in cover even if they are only partially in or behind it.