A blueprint is a map of a building. It ties the concept of design to the details required to erect a structure. Blueprints, otherwise known as architectural drawing sets, have been used since the 19th century and are a guide through the construction process. They are most commonly used by contractors to apply for building permits from the municipality within which the construction is taking place. Once the blueprints have been filed by the contractor with the building department of said municipality, they are public records and technically attainable by anyone wanting to view them.