→What is a Bosis?
# If raw meat or another [[muktzeh]] item was left on the door of one’s freezer, the door does not become a bosis. <Ref> The Gemara ([[Shabbat]] 120b) records the opinion of Rav, who forbade opening or closing a door with an oil candle built in. Tosfot (s.v. Pote’ach) explain that when the door is moved, the oil in the candle is distanced or brought closer to the wick, thereby violating Mechabeh or Mav’ir. Tosfot ask why the Gemara didn’t forbid it because the door is bosis. Their first answer is that the door can’t become a bosis, as it is nullified to the house and not to the candle. Mordechai (Siman 400) agrees.
* Although the Bei’ur Halacha s.v. Af notes that the Yerushalmi considers the door a bosis unless the candle was left there unintentionally, he suggests that the Yerushalmi is in disagreement with the Bavli. Mishna Brurah 277:4 and Kaf HaChaim 227:11 quote the Mordechai as halacha. Thus, Shemirat [[Shabbat]] Kehilchata 20:77 writes that if [[muktzeh]] is left hanging on a house or cabinet door, the door does not become a bosis. Rabbi Hershel Schachter (Halachipedia Article 5773 #22) said that the same would apply to frozen raw meat or other [[muktzeh]] items on the door of his freezer, and the door does not become a bosis.</ref>
# A basket of fruit with a rock in it shouldn’t be moved without shaking out the rock or at least spilling out everything and returning the fruit without the rock. However, if spilling/shaking out the basket will ruin the fruit one may move the basket as a whole. <Ref>S”A 309:3, Mishna Brurah 309:10 </ref>
# A purse which is made to hold money if there’s no money inside is considered a [[Kli Sh’Melachto LeIssur]] and so if there’s a key inside one may open it to take out the key. <Ref>Shemirat [[Shabbat]] KeHilchata 20:16 </ref>
# If someone places an item on someone else's non-muktzeh item it doesn't make it a bosis unless he had permission to do so.<ref>Tosfot 44b s.v. yesh, Shitah LRan 44b s.v. lo yichda, Ritva 44b s.v. lo yichda. The Ritva explains that if someone places a muktzeh on top of non-muktzeh it doesn’t become a bosis because it is considered like it was forgotten there.</ref>
# If muktzeh is on top of something that isn’t muktzeh and the non-muktzeh is servicing the muktzeh the non-muktzeh doesn’t become a bosis.<ref>Meiri Shabbat 123a s.v. gedolei explains that when the muktzeh isn’t servicing the muktzeh the non-muktzeh and furthermore if the muktzeh is servicing the non-muktzeh the non-muktzeh isn’t a bosis. Ran on Rif 23b s.v. vchen and Kol Bo 31 s.v. hatomen agree. Gra 311:26, Magen Avraham 311:23, and Mishna Brurah 311:29 codify this opinion. However, Tosfot Shabbat 123a s.v. paga answers these questions differently; he writes that it isn’t a bosis if you plan to remove it before Shabbat. Baal Hameor 23b s.v. vha agrees.</ref>
==Bosis for Muktzeh and Non-Muktzeh==
# If someone placed candlesticks and challah on his tablecloth the tablecloth is a bosis for both muktzeh and non-muktzeh. If one planned to put down challah before Shabbat and forgot there is a discussion whether the tablecloth is a bosis for both muktzeh and non-muktzeh or just muktzeh.<ref>Shemirat Shabbat Kehilchata ch. 20 fnt. 200 quotes Rav Shlomo Zalman Auerbach who is lenient if one forgot to put challot on the tablecloth that the tablecloth isn’t considered a bosis lisur rather a bosis for both. Igrot Moshe 4:73 and 3:51 disagrees since if one forgot to put on the challot it is a bosis since only muktzeh was on the bosis.</ref>