Slipcase

A box with one open side, into which a volume or a multivolume set is “slipped” for protection; publishers often issue a slipcase with two and three volume sets.

Danish: Kasette
Dutch: Schuifdoos, huls
French: Emboîtage
German: Schuber
Italian: Custodia, astuccio
Spanish: Tapas y lomo de una encuadernación
Swedish: Kassett