Warming food in an oven on Shabbat

Hi,

Under certain circumstances, one may return fully cooked food to a covered stove on Shabbat. The cover is called a "blech".

For an oven, the equivalent of a blech is a box which is closed on all sides, in which the food is placed.

(Rav Moshe Feinstein, Igrot Moshe Orach Chaim 4:74:Bishul 26-27)

המצפה לישועה,
Mordechai