If a muktzeh item was placed atop a non-muktzeh item with the intention that it stay there all of Shabbat, then the permitted item becomes muktzeh, as it serves as a basis (base) for a forbidden object. For example, if one placed money on a table, then even though the table is not in itself muktzeh, since he placed muktzeh money on it, the table becomes muktzeh because it is now a basis le-davar ha-asur. In other words, the decision to place money on the table implies consent not to use the table on Shabbat, making the table muktzeh just like the money on it. Even if the money were to fall off during Shabbat, it would not matter; since the table was muktzeh during bein ha-shmashot, it remains muktzeh all of Shabbat (SA 310:7).
In contrast, if one did not intend for the money to stay on the table over Shabbat but simply left it there by mistake, then the table does not become muktzeh, since he did not decide to make it a basis for something muktzeh. Nevertheless, le-khatĥila one should still not move the table while the muktzeh item is on it. Rather, he should tilt the table so that the money falls off and then move the table wherever he wants. However, if the muktzeh item would be damaged if it slid offupon falling to the floor, then one may move the table along with the muktzeh item to a place where the latter can safely be slid off without being damaged. For example, if the muktzeh item is a smartphone, which would likely break if dropped, one may move the table elsewhere. Similarly, if the muktzeh item is a stone, and next to the table are fragile glass items that would likely break if the stone were to fall on them, one may move the table elsewhere (Shabbat 142b; SA 309:4; SA 277:3; section 14 below).
The same applies to a laptop left on top of a book, valuable candlesticks left on a tray, valuable knives left in a case, raw potatoes left in a drawer, or a tzedaka box left on the bima. If these items were intentionally placed there, then whatever they are resting upon becomes a basis le-davar ha-asur and is muktzeh. If they were forgotten there, the base does not become muktzeh.
Sometimes, during the week, one wishes to place something muktzeh in a closet, but because there is no space he puts it on top of clothing in the closet. There is a disagreement whether such a placement renders the clothing muktzeh. Some say that since ultimately the muktzeh was consciously placed atop the clothing, the clothing becomes a basis (Taz). Others maintain that since the person did not intend for the muktzeh to be there specifically, but it simply ended up there, the item of clothing does not become a basis (MA). In practice, when necessary one may be lenient (MB 309:18).
If one finds money or other muktzeh items in his pocket, he may assume they were forgotten there, so his clothes do not become a basis. However, in order that he not continue to carry around muktzeh in his pocket, he should try to shake it out. If he is embarrassed to do so in public, or if he is worried that the muktzeh item will get lost, he may continue to wear this item of clothing until he reaches a place where he can shake out the muktzeh without fear of losing it or embarrassing himself.
. If one intended to place the muktzeh item on a permitted item for only part of Shabbat, according to Rabbeinu Tam it does not become a basis, while according to Rashi it does. SA 309:4 is inclined to be stringent, but in times of necessity one may be lenient (MB ad loc. 21). There is a similar disagreement about the law if the muktzeh item was placed atop an item in the middle of Shabbat (by the owner or with his consent). According to Tosafot, as long as the muktzeh item is there, the base is muktzeh; according to Or Zaru’a, however, it is not muktzeh. According to Rashba and Ran, if one’s intention is that the muktzeh remain there until Shabbat is over, then as long as the muktzeh item is there, the base is muktzeh as well. MB 266:26 follows those who are lenient. See BHL 310:7 s.v. “mateh.”The base becomes a prohibited basis only when it serves the muktzeh upon it; but when the muktzeh item serves the base, it does not become prohibited. Therefore, if one places a rock on a barrel to weigh down its cover and prevent it from opening, or if he places pieces of muktzeh wool on a pot to keep it warm, the barrel or pot does not become muktzeh (SA 259:1; MB ad loc. 9).
. If one intended to leave money in his pocket but decided on Shabbat that he would like to wear the clothing, what is the status of the clothing? If the garment itself is one of the sides of the pocket, as is generally the case with a shirt pocket, then the garment becomes a basis and may not be moved. In contrast, if the pocket is part of a separate lining sewn onto the clothing, as is the case with most pants pockets, the clothing does not become a basis, because the pocket is secondary to the whole garment. Thus, the pants may be moved. However, when possible, one should first shake the muktzeh item out of the pocket, taking care not to put one’s hand in the pocket or touch it from outside in order to shake the muktzeh item out. This is because the pocket itself is muktzeh (Rema 310:7; MB ad loc. 29-30; see SSK ch. 20 n. 275). If a money pouch is tied to an item of clothing, since the pouch is not sewn on, it is not secondary to the clothing, and thus the clothing becomes a basis.