card catalog
US /ˈkɑːrd ˌkæt̬.əl.ɑːɡ/
UK /ˈkɑːrd ˌkæt̬.əl.ɑːɡ/

1.
a catalog of books or other library materials, arranged on cards in drawers, now largely superseded by the online catalog
:
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Before computers, librarians used a card catalog to find books.
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The old library still has a beautiful wooden card catalog.