book cover; folding book case
Refers to a traditional protective case for books, often a folding box with clasps, used historically for scrolls or bound volumes. Rare in everyday modern Japanese.
The old sutras were kept in a folding book case.
counter for book covers
Used as a counter for book covers or cases, especially in bibliographic or antiquarian contexts. Extremely specialized and not used in ordinary counting.
This collection has three book cases.
books; volumes
The kanji 帙 is of Chinese origin, originally referring to a cloth or case for wrapping books. The reading ちつ is the on'yomi. The exact historical derivation in Japanese is uncertain, but it has been used in classical and bibliographic contexts.