The Set pieces are shaped and small-sized scenic elements.
They are usually used to create perspective views of buildings or for scenographic constructions of various types.
Like the Flats, they can be framed, that is, with a wooden or metal frame covered with muslin or other fabrics.
Or they can be built and trolleyed.
The framed Set pieces of rectangular or square shape used to cover various openings (i.e. to close them as a background) are called Backing flats.
Video & Documentation
Teatro alla Scala, ''Il barbiere di Siviglia'', Jean-Pierre Ponnelle