Under that system, each book “belonged” to several 3x5 cards. Those library cards were relatively inexpensive, since the Library of Congress was happy to sell librarians sets of cards for each book acquisition. LC cards included a proposed classification number for both LC and Dewey systems. MARC-readable tapes and other advances in modern technology also speeded up the time required to assign cards to books. Libraries which opted to accept this default classification could retire the classification librarian. Librarians only had to classify and catalogue books when an LC card was not available.

Those 3x5 cards also led to the books being assigned to a somewhat logical and predictable place on the shelf. As a result, documents were reasonably accessible to experienced patrons, and librarians had the tools they needed to assist neophytes.

However, neither the librarians nor the patrons had reason to be overly excited with the card-based systems. Too many books could be classified - and thus shelved - in two or more locations, and librarians faced difficult or arbitrary decisions when classifying books in one place or another. When faced with classifying a document which could fall into two or more categories, librarians may want to modify the existing systems, but they are bound by the rules. The problem arose frequently, since a large number of the non-fiction books fall into this category.

Special libraries sometimes tried to place books with multiple subjects in categories which most closely represented the general field of the library. As a result of this largely subjective means of classifying documents, librarians were often forced to consider how not to shelve books by field. After making a number of these arbitrary decisions, one may wonder why librarians in scientific or special libraries didn’t have second thoughts about where to place all the books - and why they didn’t just discard the entire system. They couldn’t do that, of course - until they had an alternative.

These problems were further exacerbated by the fact that libraries had to rely on those 3x5 cards. Their subject catalogues became swollen with multiple cards which were required in order to reference different aspects of the books. When books were lost, stolen, or removed from the library, they had the nightmare of finding each card from that set, including the inevitable, elusive card which had been misfiled. After seemingly interminable searches, librarians would just give up the search - thus scattering misplaced and incorrect cards throughout the catalogue. With all these problems facing understaffed yet burgeoning libraries, it seemed that the frustrating problem of tracking and accessing holdings efficiently was hopeless.