35mm microfilming of drawings up to and larger than AO can be filmed and preserved on a roll of film or each frame mounted into an aperture card, which can be titled. This format has been specially designed to produce high quality images from a wide range variety of drawings, maps and plans.

Aperture cards provide a permanent, tamper-proof record of an engineering drawing or other document and are not vulnerable to evolutionary change, which accompany other types of storage media.