Folding mechanism used in card and dining tables for expansion. The back half of the frame is cut and hinged two or more times under the extended top leaf. Concertina movement refers to a folding mechanism used in furniture design. It is named after the musical instrument concertina, which features a similar folding and expanding movement. In furniture, concertina movement is typically used in items such as folding chairs, tables, or room dividers. It allows the furniture piece to expand or collapse easily for storage or transport purposes. The concertina movement is achieved through a series of connected joints or hinges that enable the folding action.