(barrel, boom, pipe, batten) The horizontal metal tube (usually 48mm in external diameter) hung from flying lines (or forming part of a grid) from which lighting equipment and scenery etc. may be suspended. Also known as a Barrel. When vertical, known as a Boom. Sometimes known as a Pipe in the US, although many curse that usage, and demand the use of Batten ; "A pipe is what you smoke; a batten is what you hang your instruments from."