The Reinforced Door is crafted from Reinforced Stone and is an explosion resistant door that behaves like an iron door. It requires a Lever or some other form of Redstone power in order to open. It has a blast resistance of 150, the same as Reinforced Stone.
The Reinforced Door will protect from explosions even if it is open. It is most often used for safe access to Nuclear Reactors, due to the fact that, even when open, the game detects the two blocks it fills as occupied.