Cover

Cover operates similarly to shields. When defining cover, the GM and players establish which target wheels are covered and from which directions. Attacks from these directions that hit the target wheel automatically hit the cover instead (although excess damage may hit the character afterwards). Attacks aimed at target wheels adjacent to covered wheels suffer disadvantage.

Other creatures can provide cover and can therefore be hit accidentally. This most commonly occurs when you fire a ranged weapon into melee combat and the risk of doing so should be clear before making the attack. The GM determines what target wheel or hit location of the covering creature is at risk based on the orientation of the covering and covered creatures. After determining who and where the attack may hit, you redetermine the level of advantage of the attack, which may change the DC of defensive combat maneuvers for the covering creature. For example, advantage gained by taking the Aim action at an enemy would no longer apply if you accidentally hit an ally in the back.