Emphasizing the importance of the card catalog as a tool for the reference librarian, a unit of instruction was designed to supplement a course in library reference skills. Students who take the course are asked to complete certain requisite readings and to study materials dealing with the parts of the catalog card, filing rules, and assigning appropriate subject headings. Students learn to examine problems from the perspectives of library patrons and researchers. This course description includes a required reading list, a class worksheet, and homework assignments. (EMH)