Each Sanborn Map is divided into numbered sheets, each approximately 65x55 cm. If you arranged all the sheets together on the floor, you would have a complete, but very large map Because streets and buildings are located on various sheets,you need to use the key and index sheets to navigate. Maps with several sheets also include a key sheet and/or an index sheet. A key sheet provides a birds-eyeview of the city. You will be able to see sheet numbers (or volume numbers) over different areas of the town. You can then browse the sheet thumbnails to pull up the sheet you are looking for. An index sheet provides an alphabetical list of streets (usually including block numbers) and prominent buildings, labeled "specials." The index refers you to the sheet number for that address or building.