Wow! This is an excellent, fact filled nitty-gritty technical article that explains a great deal more than just Titanic's water tight doors! You did a really great job here and many questions I once had or wasn't sure of have now been cleared up. For instance myself and many other members of this site were not 100% sure about the watertight integrity of the two lateral swinging doors that lead into Hold #3 from the fireman's tunnel vestibule. Good stuff!!