Shabbat 123 - Carriages, trunks and movable closets
House construction and repairs are considered building and are forbidden to be performed on Shabbat. Therefore, a door of a house, once detached, cannot be reattached to it. Moreover, it cannot even be moved on Shabbat, since it has no use by itself, and it considered "muktzeh," something not prepared for use on Shabbat.
By contrast, utensils such as carriages, trunks and movable closets that can nevertheless be moved are not considered muktzeh and can be used on Shabbat. Even their doors, although unusable by themselves if detached, can be moved and even put back into their place. There is a different opinion, however, which considers large utensil to have the same status as houses.
The laws of other utensils also depend on their intended use. For example, one may take a hammer, usually associated with forbidden work, and use it to break nuts; a shovel can be used to scoop dried figs from the bottom of the barrel; a pitchfork can be used to give food to a child who is stranded on the other side of the river; a hand needle may be used to remove a splinter and a sackmaker's needle may be used to open a door with it. What kind of hammer do we mean? One that is used for ordinary tasks, but not a blacksmith's hammer, since it is designated only for blacksmith's work. Others say that even a blacksmith's hammer may be used for the permitted work of cracking nuts. Similar disagreements exist in regard to all items listed above.
Art: John Singer Sargent - Venetian Doorway