The circulation of collection materials to patrons. The checkout process normally involves scanning a patron's barcoded library card into an integrated library system on a staff computer at the circulation desk, scanning the barcodes on the items to the patron's account, and informing the patron of the items' due dates, with stamped cards or a printed receipt (see date due slip). Some libraries allow self-checkout. Any branch that allows borrowing is called a lending library.
A lending library may have a reference collection for encyclopedias, dictionaries, records, and other essentials, the items from which may not be borrowed.