Everyone has seen a curious youngster taking a new toy apart to see what is inside. Conversely, the designer many times finds it easier to explain a three-dimensional piece of scenery by cutting it open and showing the inner structure. The section is the draftsman's way of performing the same operation. A revealing show-all- hide-nothing view is a great time and space saver, and in the theatre, it can be used in many different ways.
The sectional view is made by cutting into the object with a cutting plane, an imaginary plane that cuts like a giant knife and divides the object into halves. With imagination one half of the object is removed exposing the inside of the other half. The cutting plane line shows the location of the cut and the arrowheads indicate the direction of the view. The location of the cutting plane is arbitrary, and if it is placed wisely, the sectional view will tell all. The cutting plane can be staggered or off set, forward and back to include a special detail. In the offset section, however, it is important to show the off set of the cutting plane line clearly so the viewer can read the section correctly.
Usually, the cutting plane is vertical and most sectional views are vertical sections. There are occasions, however, when a horizontal section is necessary. The cut-
ting plane is used in a horizontal position and the resulting section is referred to as a plan.
The floor plan of a stage set is a horizontal section with a cutting plane that is parallel to the stage floor. To expose the true shape and structure of the set, the cutting plane is passed through as many wall openings as possible. The upper portion is removed and the direction of the view is downward. There are times when the lower portion is removed to show a view looking upward, possibly at an elaborate ceiling or cornice design.