What is the function of a fly rail?

The fly rail is an essential part of stagecraft, serving as a horizontal structure that is primarily used to control scenic elements such as backdrops, curtains, and other stage scenery. It allows stagehands to raise and lower these elements smoothly and safely, using ropes and pulleys connected to the fly system. This system enables quick scene changes without obstructing the performance, as the scenic elements can be flown in and out of view. The fly rail essentially acts as the control center for these movements, ensuring that the visual aspects of a production can be managed efficiently during a show. This functionality is crucial for both the logistics of staging and the overall flow of a performance.

The other options, while they may pertain to different aspects of stage management, do not accurately define the purpose of a fly rail. For instance, it does not hold costumes, adjust lighting, or provide seating for the director, which are all handled by different components of the stage environment.