Microfilm Aperture cards, often simply called Aperture Cards were used as part of large document catalogues and allowed engineering drawings and other large format documents to be stored on microfilm attached to the punch card. Aperture cards would commonly be used as part of a document database stored entirely on punch cards. This allowed a card sorter to be used to search for a document by its document number, or other punched metadata and quickly located in a large collection of cards.