Originally constructed and operated by sailors, stage rigging owes its origins to the pulleys, knots and ropework of ships. Dating back to Leonardo da Vinci and the Court Masques of 15th-century Italy, these "hemp systems" used rope lines and sandbags to maneuver scenery and fabrics into and out of a performance area with the same technology found in boats. In the mid-20th century, a safer and less intricate form of stage rigging emerged in the form of the counterweight system.
In a typical counterweight fly system, an arbor is used to balance the weight of stage scenery and lighting suspended above stage. The arbor, carefully weighed to counterbalance the batten load, raises and lowers rigged loads as it moves up and down on a vertical track along a wall in the backstage wings. The arbor can be accessed two ways for weight adjustments: at the stage floor when the batten has been fully raised, and at a "mid-rail" or loading gallery once the batten has been lowered to the stage floor for load adjustment.
Using a fly system requires a careful calculation of the weight attributed to each "line set" or batten. Clear the stage of any other workers as you approach the fly system and carefully release the safety ring and rope lock of the line set. If the pulley rope or "purchase line" moves suddenly, reengage the rope lock and add or remove weights until the system is properly counterbalanced. If the purchase line remains stable, gently pull on the rope to bring in the stage batten, making sure that all workers have cleared the area. Carefully calculate the weight once you are complete and add or remove the required weights on the "mid-rail" or loading gallery above the stage.
The most common practice of using stage lighting with a rigging system designates four or more battens for the sole use of hanging lights. These battens, called "electrics," are wired so that multiple dimmer boxes are suspended from the pipes that correspond to various circuits and electrical connections in the theater. Line sets are "flown in" in the manner described above and then lights are suspended in the desired locations. Any gels or metal shape templates, or "gobos," are inserted in the instruments. Once each line set has been reweighed using the loading gallery, each electric is returned to its raised position and focused using a ladder.
Complicated stage shows and productions can sometimes require intricate math equations to safely and correctly suspend certain stage scenery. Examples may include: pulley systems; aerial arts, wherein a batten is temporarily weighed down by a performer; snow and confetti systems and more. In these situations, it is always preferable to have a skilled and certified technician operating any rigging machinery. The safety hazards of stage rigging are numerous, and great care should be taken when loading weights on the gallery level.