Cover and Concealment: Cover is any solid object
between an attacker and defender capable of protecting
the defender from a weapon attack. Concealment is any
object that prevents viewing or sighting of the defender.
Cover may also be concealment; concealment is not necessarily
cover.
An individual under cover cannot be attacked; an individual
in concealment cannot be attacked unless the attacker
has some reason to shoot into the area.
Individuals who attack from cover become visible and
may themselves be attacked; because they retain partial
cover they are eligible for a defending DM of -4. Individuals
who attack from concealment provide reason to believe
they are present, and may be attacked; because they remain
partially concealed, they are allowed a defending DM of -1.
