In modern armoured warfare, hull-down is a position taken up by an armoured fighting vehicle (AFV) so that its hull (the main part of the vehicle) is behind a crest or other raised ground, but its turret (or a superstructure or roof-mounted weapon) is exposed. Turret-down is the position in which the vehicle's crew can observe forward from roof hatches, but the vehicle is completely hidden (usually a few metres further back from a hull-down position). The belly armour should not be exposed, because it is vulnerable to even modest antitank weapons.