In theater, batten', barrell or pipe refers to a long metal pole suspended above the stage (and sometimes above the audience) from which lighting fixtures, theatrical scenery, tabs or other curtains may be hung. Usually these battens can be raised or lowered into a fly tower, both for ease of use, and to achieve an effect whereby the suspended items appear to "fly" in or out during a performance.
Alternatives
Some theaters do not employ this system, and instead use a static network of pipes accessible from catwalks above the stage. This is sometime considered a safer approach, as there is less chance of pipe accidentally "running" in or out, but it forces electricians, riggers, and audio engineers to carry equipment or scenery to the pipes via ladders, lifts, or ropes.
Types
Electric
An electric is a special type of batten with a cable raceway affixed above the pipe. It generally has plugs for lights (and sometimes microphones) built in which continue through a snake to dimmers or a patchbay (in the case of audio). The plugs have indentifying numbers printed on them so that they can be easily referenced by the control system. Often an electric will include non-dim circuits used for worklights or special effects. Electrics are among the heaviest types of battens, often weighing more than a thousand pounds fully loaded. Often they have large loops of spring steel extending to each side so that other battens which are swinging do not damage the lighting instruments. Electrics generally have an established trim height (a reference for standard height) so that focusing is consistent. In some theaters, especially where battens are close together, a heat resistant fabric is attached in front of the electric to prevent heat from the lighting instruments from damaging nearby flown items.
Drapery
A drapery pipe carries tabs, travelers, scrims, wings, teasers, and generic soft goods. Full-stage drapes can be very heavy, weighing hundreds of pounds, especially the grand drape. Wings or teasers however, can be comparably light as they are not usually very thick and sewn without gather.
Clouds
Many theaters have built in shells designed to reflect sound produced on stage back into the audience. These shells often include large folding panels which can be flown in.
Set
Elements of the set which are relatively flat or light can be flown in on battens.
Storage
Due to the hazard created by overhead storage, it is never suggested that theatres store scenery, lighting instruments, etc. on spare battens.