Arukh HaShulchan, Orach Chaim 302:19-303:4

Sugya Map: Defining Tashmish and Tashmish d'Tashmish

• The Issue: The parameters of Kli she-melachto l'issur (an object used for prohibited labor) and the status of items used solely for the needs of such objects (Tashmish d'Tashmish).
• Nafka Mina: Whether a secondary vessel (e.g., a case or a protective cover) inherits the issur of the object it houses.
• Primary Sources: Shabbat 123a (the gemara on klafim), Orach Chaim 308:3, Arukh HaShulchan 302:19-20.

Text Snapshot

Arukh HaShulchan, 302:19: "אבל כל דבר שאינו כלי כלל, אלא שהוא תשמיש דתשמיש של כלי... מותר לטלטלו."

• Leshon Nuance: The Riaz (cited by the Arukh HaShulchan) distinguishes between the tashmish (the primary vessel) and the tashmish d'tashmish (the secondary container). The dikduk here hinges on the definition of "Kli"—if the object lacks independent utility, it is batel to the status of the item it protects.

Readings

• Rambam (Hilkhot Shabbat 20:1): Asserts a sweeping categorization: anything that is not a kli is not subject to muktzah restrictions, provided it serves no independent function.
• Arukh HaShulchan (302:20): Offers a chiddush of practicality: If the "secondary" item is inherently valuable or useful (e.g., a sturdy box), it regains the status of a kli and is subject to muktzah laws regardless of its "secondary" nature.

Friction

• Kushya: If tashmish d'tashmish is mutar, why are we stringent with neirot (candles) and their boxes?
• Terutz: The Arukh HaShulchan argues that neirot are muktzeh machmat gufo (intrinsic prohibition), whereas the tashmish rule applies only to muktzeh machmat melachto (instrumental prohibition).

Intertext

• Shulchan Aruch, OC 308:3 (on tashmish d'tashmish).
• Mishnah Berurah 308:12: Emphasizes that if the secondary vessel is "made for" the primary, it shares the issur.

Psak/Practice

The Arukh HaShulchan effectively narrows the tashmish d'tashmish leniency. If you use a protective case, its status is determined by its own utility. If the case is useful in its own right, it is muktzah as a Kli she-melachto l'issur regardless of what sits inside.

Takeaway

Functional utility trumps structural hierarchy; if it holds something "prohibited," the container itself is judged by its own independent capacity for use.