* Magen Avraham 253:31 permits Shehiya in an oven because the fire is covered by a cement or clay wall built into the oven based on the S”A 253:3 who permits leaving on the fire if there’s an empty vessel separating between the fire and the food. However, the Magen Avraham adds that based on the Maharil (Minhagei Maharil pg 36; see 318:15), Agudah, and Tashbetz 27 the flame must have some interposition such a wooden plank that serves as a reminder besides being covered by metal. The Achronim unanimously agree including Eliyah Rabba 253:31, Tosefet [[Shabbat]] 253:40, Shulchan Aruch HaRav 253:26, Aruch HaShulchan 253:25, Mishna Brurah 253:81, and Chazon Ovadyah ([[Shabbat]] 1 pg 50).
* According to this, a metal covering of the fire which also serves as a reminder would permit the fire to be used. Therefore, Sh”t Igrot Moshe 1:93 writes that a gas stove when covered with a metal sheet, commonly referred to as a Blech, is like a covered Kirah and is permissible. Shemirat [[Shabbat]] KeHilchata 1:63 and specifies that the cover should be something that’s not usually used to cover a fire. Sh”t Zera Emet O”C 253:26, Sh”t Maharam Brisk 2:76, Sh”t Tefilah LeMoshe 1:37 (also recorded in Menuchat Ahava Ahava 3:1 in Rabbi Moshe HaLevi), Shem Chadash (on Yereyim 1 pg 58), Kaf Hachaim 253:11, Sh”t Maharshag 2:50, Sh”t Divrei Chizkiyah 1:2 in name of Mahari Shari, Sh”t Yaskil Avdi O”C 3:10(2), Sh”t Ohel Yosef (Rabbi Yosef Parid; Siman 10), Rav Vosner in Sh”t Shevet HaLevi 1:91, and Chazon Ovadyah ([[Shabbat]] 1 pg 50) concur.
* [Chazon Ish 37:9 argues on the Mishna Brurah from Rashi ([[Shabbat]] 37a D”H Gaba; quoted by the Tur) who forbids a covering over an empty space and concludes that a covering that’s not normally used and lowers the heat of the fire is considered a covering. Thus, a covering on our modern stove wouldn’t be sufficient. Chazon Ovadyah (vol 1 pg 51), Sh”t Shevet Levi O”C 1:91, Toldot Zev ([[Shabbat]] 2 pg 192) argue on the Chazon Ish that Rashi is referring to a [[cooking]] on [[Shabbat]] in a way that’s usual and so a covering it’s sufficient, however but by Shehiya one only needs a reminder not to stoke the coals and once it’s an unusual interposition it doesn’t need to lower the heat of the fire. See Bach 253:14 s.v. VeDavka and Sh”t Maharam Shik O”C 117 who also make this distinction. Rabbi Hershel Schachter (in The Laws of Cooking and Warming Food on Shabbat p. 181) writes that the minhag is to allow leaving food on a blech before Shabbat unlike the Chazon Ish.]* '''Knobs:''' Sh”t Igrot Moshe O”C 1:93, Sh”t Tzitz Eliezer 7:17(3), Sh”t Bear Moshe vol 7, and Yalkut Yosef ([[Shabbat]] vol 1 pg 96) add that besides covering the flame it’s preferable to cover the knobs also. Orchot [[Shabbat]] (vol 1 2:9, pg 65) quotes Rav Shlomo Zalman Auerbach and Rav Elyashiv (who is also quoted by Hilchot [[Shabbat]] BeShabbato pg 197) who hold that a covering of the knobs isn’t necessary if the fire is covered.
* On the other hand, Rav Aharon Kotler (quoted by The Laws of Shabbat p. 338 fnt. 800) and Rav Soloveitchik (quoted by Rav Schachter in The Laws of Cooking and Warming Food on Shabbat p. 181) held that covering the knobs is the primary way to avoid the issue of not coming to adjust the temperature and covering the fire is an added stringency. </ref>
# Some consider a hotplate or electric hotplate (plaata) a covered fire and others consider it an uncovered fire. <ref>