You use a
ranged weapon to target a limited area (such as
a doorway, a hallway, or the eastern side of the
clearing) and make an attack against the next
viable target to enter that area. This works like a
wait action, but you also negate any benefit the
target would have from cover, position, surprise,
range, illumination, or visibility. Further, you
inflict 1 additional point of damage with the
attack. You can remain on overwatch as long as
you wish, within reason.