There are two main theories on how the ship broke in two — the "top-down" theory and the Mengot theory, so named for its creator, Roy Mengot. The more popular top-down theory states that the breakup was centralized on the structural weak-point at the entrance to the first boiler room, and that the breakup formed first at the upper decks before shooting down to the keel. The breakup totally separated the ship up to the double bottom, which acted as a hinge connecting bow and stern. From this point, the bow was able to pull down the stern, until the double bottom failed and both segments of the ship finally separated. The Mengot theory postulates that the ship broke due to compression forces and not fracture tension, which resulted in a bottom-to-top break. The double-bottom would have failed first and been forced to buckle upwards into the lower decks, as the breakup shot up to the upper decks. In this model, the ship was held together by the B-Deck, which featured 6 large doubler plates — trapezoidal steel segments meant to prevent cracks from forming in the smokestack uptake while at sea — which acted as a buffer and pushed the fractures away. As the hull's contents spilled out of the ship, B-Deck failed and caused the aft tower and forward tower superstructures to detach from the stern as the bow was freed and sank.