3. Cutting, tearing, or breaking an item in order to make a use with it:

Important Note: There are several prohibitions that can be involved in cutting an item on Shabbos. These are: Destroying, Fixing a vessel, Tearing, Grinding, Erasing. Below we will deal with only the aspect of Tikkun Keli-fixing- involved in cutting. For the full details, final rulings, and practical Q&A on this subject please refer to “The Laws of Cutting and Tearing an item on Shabbos”!

Cutting an item with a knife to make a use with it:[1] Although cutting items detached [from the ground] is initially permitted when one is not particular to cut it in a specific measurement, as explained in chapter 314 [Halacha 16[2]] nevertheless if through doing so one fixes the item to be used for a certain use, then he is liable for [the] “fixing a vessel” [prohibition] if he cut it using a knife, as was explained in chapter 322 [Michaber Halacha 4] regarding the cutting of a twig.[3]

Tearing it with ones hands to make a use of it:[4] If it was done without a knife then one is exempt [from Biblical liability], although it is [Rabbinically] forbidden.

Breaking earthenware and tearing paper for a use:[5] Therefore one may not break earthenware and may not tear paper which is permitted to move [i.e. is not Muktzah] in order to use the [torn or broken piece] for a use due to that doing so is similar to him fixing a vessel. See Chapter 508 [Halacha 2[6]]

May one break a piece of material off a broken vessel in order to use it for a purpose on Shabbos?[7] A vessel which has become damaged [and is thus no longer in use] one may not detach from it a piece of earthenware to use to cover something with or to place something on, being that doing so is like making a vessel, as any item which one fixes on Shabbos for it to be useable for any use transgresses the prohibition of “Tikun Keli” [making a vessel on Shabbos].

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[1] Admur 340:17; See Michaber 340:13; M”B 322:13

[2] There it is explained that cutting wood to a desired measurement is Biblically forbidden.

[3] This will be brought below in Halacha 4

[4] Admur 340:17; See Michaber 340:13; M”B 322:13

[5] Admur 340:17

[6] There Admur brings different cases that tearing or breaking an item is forbidden due to one making it now fit for a use.

[7] Admur 308:82

[8] Accordingly, one must say that all the other cases discussing Tikkun Keli when tearing something [earthenware/leaf for drainpipe] must be referring to when one does so with a knife, as only then is he liable, or perhaps even with one’s hands and Admur means to say it is Rabbinically forbidden. Vetzaruch Iyun as if it is common to cut something with one’s hands versus a knife, such as plucking a leaf, should this not be Biblically forbidden?

[9] Pashut! See Admur 308:54 that if shorten is Tikkun Keli. However, see Tzitz Eliezer 13:45 that when one does not care of the size of the cut then it is not Tikkun Keli