CUL's off-site collections are organized differently from those on campus. Onsite, campus collections are separated into discrete units demarcated by interior space, shelving and classification. They are organized for efficient and comfortable browsing, retrieval and re-shelving. Onsite collections are often high-use and organized to allow active, dynamic use by patrons.
ReCAP is a high-density storage facility that is designed for maximum efficiency storage and retrieval of low-use material. There is no patron physical access for browsing or retrieval. Call numbers are irrelevant; all items are organized by barcode and shelf location. All books are sorted by size and placed in cardboard trays. The fundamental unit of high-density storage is the tray. Books are put into cardboard trays, several of which fit on a single shelf. All items in the same tray must be assigned identical customer code. Items from separate library collections may occupy the same tray if they share a customer code. If collections have different customer codes, they must be put in different trays. Trays with different customer codes may be accessioned on the same shelf. In this way, library collections in high-density shelving are intermingled.
Every customer code has several elements, enumerated in the customer code table. Each code can describe a collection and/or campus delivery location. The CUL system of customer codes appears complex because of the large number of departments, collections and delivery options. Some codes are used only for physcial collections; some codes are used only for delivery; others represent both collection and delivery option.