Translation:Shulchan Aruch/Orach Chaim/259
1. Several Laws Governing Insulation and Moving the Insulating Materials, 7 Seifim: Since they are muktzeh, on Shabbos, it is forbidden to move muchin (any soft substance, e.g., cotton, the soft wool of an animal, or the remnants of worn out clothes.” In this section, we are speaking about muchin that are dry, for muchin that are wet are considered as substances that increase temperature and are forbidden to be used for insulation) that were used on Friday to insulate a pot on the spur of the moment. Rather, he should shake the cover and it will fall (on its own) e.g, its muktzah is uncovered, and this is not considered 'moving'. However, if it was insulated with fleece wool, even if it was not designated for that purpose, it is permitted to move it. This refers to fleece that is not set aside for commerce. However if they are for merchandise they must be set aside. If one insulates with them without them being set aside, one shakes the cover and they fall off, that is to say, when the cover of the pot is considered as a k’li. Even though they are on top of it, we are not worried about it, because we do not make a Basis for them.
2. Those who place stones and bricks around a pot (for insulation) must permanently designate them for that purpose (so that it will be permitted to move them on Shabbat). For as long as they are not designated for that purpose, they are not considered important to a person and he may cast them away. Therefore, it would be forbidden to move them if they were not set aside and designated for that purpose
3. When a person insulated [a pot of food] in a container full of muchin that are forbidden to be moved, once he removed the pot from there in the prescribed manner, he may return it there, as long as the hollow [in which the pot had been placed] remains intact. If, however, the hollow did not remain intact, it is forbidden to return it. Nevertheless, as an initial preference, one may remove the pot with the intent of returning it, [provided the hollow remains intact]. We are not concerned that he may widen the hollow if it does not remain intact. There are those who say that even if one insulates with a substance that is permissible to move, if the hollow remains intact one may not return it, because the pot would need to have a place made for itself to be grasped, as we find regarding one who insulates on Shabbat.
4. One who insulates with something that is not taken away and covers its mouth with something that is not removable, one exposes the cover, grabs the pot and removes it.
5. One who insulates and covers (a pot) with something that is not removable, if the muktzeh of the pot is exposed, one removes it and returns it, and if not we do not remove it.
6. When a festival falls on Friday, there are those who forbid insulating with stones, because this is like Binyan; and there are those who permit this.
7. When something warm is placed in an oven for Shabbos and the opening of the oven is blocked with a board which is sealed with mud, it is permitted to break apart that seal on Shabbos to remove the warm food, and to return it and seal it. If it has burning coals, it is permitted to be done by a non-Jew. RAMA: There are those who are stringent not to allow a Jew to break the seal of the oven sealed with mud if it is possible to get a non-Jew to do it. If it is possible to have a minor Jew do it, an adult Jew should not do it. If it is not possible, then an adult can do it in a slightly different manner than usual, and this is our custom. And it seems to me that it is permitted to return it and seal the over, in other words during the day, for then all the pots have been cooking like they have needed. However at night, close to the time he insulates it - for there is a doubt that maybe the pots have not yet cooked fully - it is forbidden to seal the oven because one will cause [the food] to cook more quickly as is explained in Siman 257 Seif 4. Even doing so via a non-Jew is forbidden, as explained above at the end of Seif 253 (and for other laws regarding Chazarah on Shabbat see later Siman 318).