Fashioning Openings to Utensils on Shabbat by Rabbi Chaim Jachter


Last week we discussed the debate among Poskim whether one may open a can on Shabbat.  This week we will explore the prohibition of creating openings to utensils on Shabbat.  The debate surrounding the scope of this prohibition has many practical ramifications for our observance of Shabbat.  We will discuss the debates concerning the permissibility of opening cardboard cartons, bottle caps, children’s juice boxes and peel-off seals.  It is important to note from the outset that the best practice is for one to avoid encountering these issues, and to open on Erev Shabbat any items that one anticipates will be needed on Shabbat (see Shemirat Shabbat Kehilchata 9:note 1). 

The Prohibition to Fashion Openings – Old and New Hole

The Gemara (Shabbat 146a) notes the biblical prohibition to fashion a new opening on Shabbat.  The Gemara, however, does permit reopening an “old (preexisting) hole.”  Rashi (s.v. Nekev Yashan) explains that the Gemara speaks of an “old hole that was sealed, that when one reopens the hole he is not considered to be creating a hole, because the hole has been created and the prior sealing of the hole was insignificant.” 

Accordingly, it is biblically prohibited to puncture holes in a metal juice or baby formula can.  The holes created are unquestionably “new holes.”  Some Poskim also note that when one removes the “ring tabs” from certain orange juice containers that he creates a new opening.  These Poskim claim to have verified with the manufacturers that there is no preexisting opening on the orange juice container.  Thus, one creates a new opening when opening these orange juice containers.

It is somewhat difficult, though, to determine what is an “old hole.”  For example, Halachic authorities debate the permissibility of opening the glued spout of a cardboard carton on Shabbat.  Rav Moshe Feinstein (Teshuvot Igrot Moshe Orach Chaim 4:78) rules that it biblically forbidden to open the spout of such a carton on Shabbat.  Rav Moshe writes, “even though the milk cartons has a preexisting hole, the opening is sealed thoroughly and the original opening is nullified.  Thus, when one opens the spout, he creates a new opening.”   Rav Simcha Bunim Cohen (The Laws of Yom Tov, p.186) notes that even Rav Moshe would permit puncturing the bottom of the container, thereby ruining the container, and then tear open the top of the carton and pour out the contents.  See Shemirat Shabbat Kehilchata 9:3, footnote 20, where Rav Shlomo Zalman Auerbach and many other major Poskim are cited as agreeing with this idea. 

On the other hand, Teshuvot Migdalot Merkachim (number 36, cited by Rav Simcha Bunim Cohen, The Laws of Yom Tov p.186) believes that it is essentially permissible to open the spout of a cardboard carton on Shabbat.  His assessment of the situation is that the spout already exists but that it is temporarily closed somewhat so that the contents do not leak from the container.  The Debretziner Rav (Teshuvot Beer Moshe 6:89) essentially agrees with this assertion.  Both of these writers, though, advise following the strict opinion on this issue.  Rav Yosef Adler reports that Rav Yosef Dov Soloveitchik subscribes to the lenient view on this issue. 

Bottle Caps

Poskim in the past two decades have vigorously debated at considerable length the permissibility of opening a twist-off bottle cap that breaks when unscrewed.  Rav Shlomo Zalman Auerbach (Teshuvot Minchat Shlomo 1:91:12) rules that it is forbidden to open such a bottle cap on Shabbat, since by doing so one creates a functional bottle cap.  He explains:

Even if one should break the container and remove all of its pieces from the bottle cap, as long as the bottle cap is connected to its bottom ring, it cannot serve as a bottle cap for another container.  Accordingly, it becomes a functional bottle cap only when one twists the cap and thereby removes the bottom ring from it.  Hence, opening the bottle cap constitutes an act of ‘creating a vessel’ (Tikkun Kli).

Rav Shlomo Zalman cites the Shulchan Aruch (O.C.322:4) as a precedent to this ruling.  The Shulchan Aruch forbids removing a splinter from a piece of wood to use to use as a toothpick, because doing so constitutes a forbidden action of fashioning a Kli.  Rav Shlomo Zalman claims that twisting open the bottle cap similarly fashions a functional bottle cap. 

Rav Moshe Feinstein (cited by Rav Efraim Greenblatt, Teshuvot Rivevot Efraim 4:189) and Rav Rav Yosef Shalom Eliashiv (cited in Shalmei Yehuda, p.104) are among the prominent Poskim who concur with Rav Shlomo Zalman’s strict ruling. 

On the other hand, many prominent Poskim rule leniently regarding this question.  Rav Ovadia Yosef (Teshuvot Yechave Daat 2:42) and Rav Eliezer Waldenberg (Teshuvot Tzitz Eliezer 14:45) are among the major Poskim who subscribe to the lenient approach to this question.  Rav Ovadia and Rav Waldenberg argue that the bottle cap is a functional bottle cap even before one removes the bottom ring.  They point out that it serves as a bottle cap for the bottle it is covering.  Thus, the fact that before it is broken it cannot serve as a bottle cap for another container is irrelevant.

Moreover, Rav Waldenberg questions the analogy to the Shulchan Aruch’s ruling that forbids taking a splinter from wood to serve as a toothpick.  He argues that the two cases are not comparable because the bottle cap is designed to have its bottom ring removed, thus one is not creating a new Kli. 

Rav Waldenberg adds that one’s intention when opening the bottle cap is simply to gain access to the drink and not to create a bottle cap. He writes, “No one opens a container in order to obtain a useful bottle cap for a different container.” 

Rav Ovadia Yosef develops this theme further.  He cites a very fundamental insight of the Maggid Mishneh that appears in his commentary to the Rambam, Hilchot Shabbat 12:2.  The Rambam writes that if one extinguishes metal in water he violates a Torah prohibition of Mechabeh (extinguishing) only if his intention is to temper the metal.  The Maggid Mishneh asks why does the Rambam require intention to temper the metal in order to violate the prohibition to extinguish on Shabbat.  Does not the Gemara state many times that one is responsible for an inevitable action even if it is not his intention for that act to happen (Pesik Reisha)?  The Maggid Mishneh answers that one is regarded as fashioning a utensil only if this is his intention.  In this case, if he does not intend to temper the metal he is not responsible for having done so, even if it is inevitable that it will happen. 

The Maggid Mishneh’s comments are cited by the Magen Avraham (318:36).  The Ohr Sameach (commenting to Rambam Hilchot Shabbat 12:2) describes the Maggid Mishneh’s assertion as “a profound insight” and “a precious jewel.”  The Ohr Sameach explains that intention in this case defines the act.  Tempering metal is usually entirely removed from one’s purview and thus one is not responsible for tempering metal unless he has specific intention to do so. 

Rav Ovadia reasons that the same applies to opening the bottle cap.  The fact that one creates a functional bottle cap for another utensil is beyond one’s purview, as he opens the bottle.   Hence, he is not defined as creating a bottle cap, since creating a bottle cap is entirely beyond his purview.  Rav Ovadia concludes, though, that it is best to accommodate Rav Shlomo Zalman’s opinion and open the bottle before Shabbat.  Rav Waldenberg offers as an alternative solution, that one discard the bottle cap immediately after removing it.  This concretely demonstrates that he does not intend to create a functional bottle cap for another utensil.

Interestingly, Rav Shlomo Zalman modifies his original ruling in his emendations and addenda to Shemirat Shabbat Kehilchata (number 61).  Rav Shlomo Zalman writes that one may be lenient in a case where it is obvious that the bottom ring is distinct from the rest of the bottle cap.  In such a design, the cap is clearly functional and complete even before it was sealed onto the bottle.  Rabbi David Ribiat (The 39 Melachot p.838-839 and footnote 78) writes that he believes that this comment of Rav Shlomo Zalman seems to apply to the caps of the plastic milk bottles that are currently used.  Rabbi Ribiat cautions that technology in our times changes rapidly and the Halacha might change with even the slightest change in the packaging design.

Children’s Juice Boxes

Both Rabbi Ribiat (The 39 Melachot p.838) and Rabbi Simcha Bunim Cohen (The Laws of Yom Tov p.191) permit puncturing the top of children’s juice box on Shabbat.  Rabbi Ribiat explains:

The containers are disposable and usually discarded immediately after use.  Puncturing the box to insert a straw is not Assiyat Petach (fashioning an opening) because there is no need for a proper spout, but merely for a simple opening.  The puncture-hole in the cardboard exterior of the carton is factory made; the interior foil lining that one punctures is thus comparable to a wrapper.

Peel-off Seals

Rabbi Simcha Bunim Cohen (ibid.) permits one to remove peel-off seals on Shabbat.  These seem to be analogous to the Tosefta’s (cited by the Mishna Brurah 314:25) permission to remove the leather from the top of a wine barrel if he does not intend to create a spout.  Removing the seal does not create an opening.  It merely constitutes removal of the cover of the spout; just as removing the leather is regarded as merely removing the cover of the top of the wine barrel.


We have discussed some of the major issues that arise regarding creating openings in utensils on Shabbat.  Our discussion of these matters, however, is far from exhaustive.  Many more issues remain to be discussed regarding opening various items on Shabbat.  New issues will almost certainly arise in this context during the next few decades.  We must be alert to notice an activity that is questionable and present the issue to a competent Halachic authority.  We shall conclude with the advice that we presented at the outset of this essay – one should try to open on Erev Shabbat any item he anticipates he will need on Shabbat.

Lechem Mishneh by Rabbi Chaim Jachter

Opening Cans on Shabbat by Rabbi Chaim Jachter