A multiplex refers to any movie theater with five or more screens. (In exhibition parlance, a two-screen theater is a twin, a three-screen is a triplex, and a four-screen is a quad. Much of the following article describes practices prevalent with these exhibitors as well.)
The economics of the multiplex introduced a substantial degree of automation to the projection booth. Because one projectionist would be responsible for many shows simultaneously, the multiplex model leaned heavily on the use of automation systems, xenon lamps, platters, make-up tables, foil cues,shoe polish, interlocking, Kelmar cleaners, lens turrets, and more.
Multiplex projection practices arose in an era when studios produced hundreds or thousands of prints for a typical release, and the consequences of damaging an individual print were very low. Given the radical shift in the exhibition landscape spurred by the introduction of DCP, all surviving film prints should now be treated as archival objects. Many of today's projectionists gained substantial experience working in a multiplex environment. This expertise is valid and valuable, but may include certain habits and philosophies that do not reflect archival best practices.