06. Permitted and Prohibited Implements

Just as Boneh and Soter apply to building or demolishing a house, the ground, or an ohel, they also apply to building or demolishing an implement.[5] Therefore, one may not insert the handle of a hammer into the hammer head or a broom handle into the broom shaft. A permanent insertion is prohibited by Torah law, while a temporary insertion is forbidden rabbinically. Similarly, it is prohibited by Torah law to put together a bed or chair using nails, screws, or glue, since such attachments are full and permanent. Fixing a chair leg or table leg that has fallen off is also forbidden, as is attaching or removing a rubber chair tip or table tip (a rubber protector that goes underneath a chair leg or table leg).

If there is a possibility that people will forget it is Shabbat and end up fixing the implement, the Sages forbid moving it. For example, if a leg falls off a chair or table, one may not move the item and prop it up on another piece of furniture, because someone might see it and decide to repair it. However, if the implement would be complicated to fix, or if it had already been used in this manner before Shabbat, there is no concern that he will forget and repair it on Shabbat, so it may be moved (SA 313:8; Rema 308:16; MB ad loc. 69; SSK 20:44).

One may use implements on Shabbat whose normal usage involves screwing or unscrewing. Thus, one may screw a lid on a jar, salt shaker, or pressure cooker, put on jewelry whose ends screw together, or look through binoculars that are focused by turning a knob. Since this is the normal way of using these devices, screwing and unscrewing them is not considered a melakha. However, one may not unscrew something if it unusual to do so. For example, one may not unscrew the knob of a pot cover (SHT 313:32; MA states that the prohibition is by Torah law, while Taz maintains that it is rabbinic).

Most poskim allow adjusting the height of a lectern (“shtender”) by loosening a knob and tightening it at the desired height, as this is the normal usage and the lectern remains usable at every stage of the adjustment (Orĥot Shabbat 8:9 citing R. Shlomo Zalman Auerbach and R. Yosef Shalom Elyashiv; Yalkut Yosef 314:2).

One may adjust a baby carriage or stroller with hinges or latches from an upright position to a horizontal one and vice versa. However, if doing so involves removing screws that hold the seat in position and then screwing them back in, it is forbidden because it entails making a strong attachment that is adjusted only infrequently (SSK 28:50).


[5]. Beitza 22a states that “Beit Shammai maintains that Boneh and Soter apply to kelim, while Beit Hillel maintains that Boneh and Soter do not apply to kelim.” The halakha follows Beit Hillel, as Rava rules in Shabbat 122b. However, we find in Shabbat 102b that according to Rav, one may not insert the wooden handle into the metal blade of a scythe as it constitutes Boneh. Tosafot ad loc. (s.v. “hai”) explain that in a case of bona fide assembly, Boneh and Soter apply to implements as well. The statement that Boneh does not apply to implements refers to loose attachments, as I wrote in the main text. This is also the opinion of Smag, Rosh, and Tur. Ramban, Rashba, and Ritva (on Shabbat 102b) maintain that one may not build an implement in its entirety because of Boneh, but adding onto an implement is prohibited because of Makeh Be-fatish. Rashi Shabbat 74b and Yere’im maintain that even creating an implement is prohibited on account of Makeh Be-fatish, not Boneh. The practical significance of this halakhic disagreement is when it comes to Soter. If the prohibition is on account of Makeh Be-fatish, then undoing one’s actions is not prohibited by Torah law, as Soter is defined as undoing an act of Boneh. Therefore, if undoing what was done to an implement is necessary for Shabbat, according to Ramban and those who follow his approach one may do so, while according to Rashi and those who follow his approach it would even be permitted to take the entire implement apart. However, according to Tosafot and Rosh, this would be forbidden even for a Shabbat need. Only when dealing with a low-quality implement (such as a mustekei – a barrel made of an inferior material) would it be permissible to take it apart for a Shabbat need, as explained below in section 11. SA 314:1 rules in accordance with Tosafot and Rosh. However, in 314:7, in the context of asking a non-Jew to break a vessel for a Shabbat need, it is lenient in accordance with Rashi and those who follow him. The justification for this leniency is that two mitigating factors are involved: asking a non-Jew to do melakha on Shabbat (which is only a rabbinic prohibition) and a Shabbat need (for example, if the fruits in the vessel are otherwise inaccessible). See Menuĥat Ahava 3:23:32. Rambam (MT 10:13) follows Tosafot, maintaining that Boneh applies to implements. On the other hand, he permits breaking a barrel to get to the food inside it, even if the barrel is not considered a mustekei (MT 23:2). See Kaf Ha-ĥayim 314:5.
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