A manhole is a large opening for access to sewers and other things underground. It's a hole, and it's big enough for a man, thus the name.
The meaning of ?gmanhole?h is exactly what RonBee said. In modern cargo ships there are a lot of manholes to access tanks. Starboard and port decks are fitted with side tanks as well as on tanktops - The plating forming the top of the double bottom. It is fitted to the tops of the floor plates, longitudinals and center keelson, and makes a complete inner skin extending over the bottom and sometimes up the sides of a vessel. Link to explanation of tanktop: http://titanic-model.com/glossary/p.shtml
I think, if SS Titanic was fitted with double bottoms and bulkheads -A term applied to any of the partition walls used for subdividing the interior of a ship into the various compartments. The main partition walls also serve as strength members of the ship÷Ő structure and as a protection against water passing from one compartment to another - it would not have sunk so fast. Link to explanation of bulkhead: http://titanic-model.com/glossary/b.shtml
Just remember it as a hole for a man.
By the way, women in USA have been fighting for sexes equality. Chairman becomes chairwomen, now chairperson.
Should we change ?gmanhole?h, to ?gwomanhole?h, or ?gpersonhole?h? (just kidding)
Something wrong with my previous msg - repost part of it
The last paragraph should be read as "Should we change 'manhole', to 'womanhole', or 'personhole'? (just kidding)"