Main deck
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/64/USS_Wainwright_%28DLG-28%29_underway%2C_circa_in_1971.png/400px-USS_Wainwright_%28DLG-28%29_underway%2C_circa_in_1971.png)
The main deck of a ship is the uppermost complete deck extending from bow to stern.[1] A steel ship's hull may be considered a structural beam with the main deck forming the upper flange of a box girder and the keel forming the lower strength member. The main deck may act as a tension member when the ship is supported by a single wave amidships, or as a compression member when the ship is supported between waves forward and aft.[2]