accordionfold

An accordionfold, also known as a concertina fold or zigzag fold, is a method of folding a sheet to produce a pleated strip that can expand and contract. The pleats resemble the bellows of an accordion, which gives the fold its common name.

The fold consists of a sequence of alternating valley and mountain creases. When extended, the panels form a continuous strip; when collapsed, the strip folds into a compact stack. Folds are typically evenly spaced and aligned with the material's grain to improve durability.

Materials used include paper and light cardstock, though thin plastics can be folded similarly. Many accordion folds are pre-scored at the factory to ensure uniformity, and ends may be glued or slipped into covers. This fold is favored for presenting large information in a small footprint.

Applications include promotional brochures, maps, catalogs, and posters, where multiple panels must be viewed in sequence. It is common in artist books, signage inserts, and some packaging. In crafts and origami, the accordion fold serves as a flexible backbone for more complex structures.

Variants and related terms include the concertina fold (often used interchangeably) and the zigzag fold. Related folding systems in printing include the gatefold, which creates a double-opening effect but uses different panel geometry.