On a web press—especially one utilizing a zero-speed splicer to splice together rolls of substrate—a set of pneumatically-controlled, collapsible rollers through which an unwinding web of paper snakes. With enough paper stored in the festoon, the press can draw from that supply while the unwinding roll is stopped and spliced to a fresh roll. See Zero-Speed Splicer.
A festoon is also required to give the web of paper a long lead time into the press, to provide a tightly-wound paper roll enough time to retain its original dimensions. See Festooning.