.A sectional drawing is a view, sometimes in 2D or 3D, of the cross section of a building.  Geometriclly, it is a horizontal orthographic projection of a building on to a vertical plane, with the vertical plane cutting through the building in the same way that a "floor plan" cuts a horizontal plane to view the building.

 

Section drawings are used to describe the relationship between different levels of a building. In the section view, the cut line is "boldly" drawn to show the objects that are cut through and anything beyond that is in a thinner line. Click on pictures to access informational artiles on this important building topic.