Filler, fill or sound fill
EN: Filler, fill or sound fill
Filler is scrap film, most often used to keep a sound track running the same length as the picture, even though there is just silence. When used this way in can also be called sound fill. Filler is usually a print with the emulsion scraped off the center all the way along, perhaps to prevent bootlegging, but also useful in that a mark can be seen on both sides through this wide scratch.
The Pollio Folio - Glossary of Cinematography Terms