Unless sub-wings or a non-rectangular outline floor plan exists such a wing makes the building L-shaped or T-shaped "in plan" (shape from above/below), though if not central nor at one end of the building the T-shape will be an offset T.  Where a building is aligned closely to cardinal compass points, such a wing may be more informatively described by its related side of the building (such as "south wing of the building").
This passage describes how a wing's shape is determined by its location in relation to the main building and the presence of other wings.  The description of a wing can be more specific if it is related to a particular side of the building (e.g., "south wing").