Belt armor

Belt armor is a layer of heavy metal armor plated onto or within the outer hulls of warships, typically on battleships, battlecruisers and cruisers, and aircraft carriers.

The belt armor is designed to prevent projectiles from penetrating to the heart of a warship. When struck by an artillery shell or underwater torpedo, the belt armor either absorbs the impact and explosion with its sheer thickness and strength, or else uses sloping to redirect the projectile and its blast downwards.