is a typical element of a theatrical rigging system installation. Building and fire codes typically require that either a fire curtain or water deluge system be installed to separate an audience from the stage in the event of a fire. Types Fly systems are broadly categorized as manual or automated (motorized). Manual fly systems are more specifically categorized as "hemp" (a.k.a. rope line) or "counterweight" systems. "Hemp houses" (a reference to the manila hemp once most commonly used to make the ropes) exclusively use the centuries-old tradition of ropes, pulleys and sandbags to fly theatrical scenery in and out. Hemp rigging incorporates many nautical rigging techniques and equipment (e.g., block and tackle), and was once thought to have stemmed from the nautical rigging. However, recent research has shown that this is not the case, Counterweight rigging evolved separately from hemp rigging and generally handles scenery in a more controlled fashion. Counterweight rigging replaces the hemp rope and sandbags of rope line (hemp) rigging with wire rope (steel cable) and metal counterweights, respectively. Those substitutions permit the flying of greater loads with a high degree of control, but with a loss of flexibility inherent to most hemp systems. Flexibility is lost because most components of a hemp system may be repositioned, while counterweight system components are relatively fixed. Old "hemp houses" lacked counterweight rigging, but today most manual rigging houses use a combination of counterweight rigging and, at least some, hemp rigging. For example, theaters that incorporate built-in, grid-based counterweight fly systems often will also support additional, spot hemp system line sets for spot-rigging (to spot something, in theatre jargon, simply means to (re)position something). Manual rigging is also possible with hand (and drill-operable) hoists (winches), but relatively limited operating speeds preclude their use for most running applications. Automated systems are becoming more prominent. They have the potential advantages of relatively high precision, speed and ease of control, but tend to be significantly more expensive than manual systems. Hoists of various types (e.g., line shaft, chain motor, etc.) are used. A conventional counterweight system may be automated by the incorporation of a motor and controls, in what is commonly called a motor-assist system. By using counterweight in such a manner, motor sizes can be kept relatively small. The use of a particular type of fly system in a theater usually does not preclude the use of other rigging methods in the