To the editors:
In response to your Reader to Reader inquiry (July 23) about "Let Us Make Your Blech," let me helpfully respond.
The tenets of Orthodox Judaism forbid cooking on the Sabbath. They do not, however, enjoin the keeping of precooked food warmed up throughout the Sabbath, so long as the warming process is continuous (i.e., one may not remove warmed-up food, let it cool completely down, and then return it to the burner to be rewarmed).
Further, the fire, or heating element, must be covered by something not normally used for cooking on, e.g., a metal sheet. This sheet is called a "blech."
The word "blech" is simply Yiddish for "tin," since its origin probably dates back to a time when a tin plate was the most readily available sheet metal. Today, observant American Jews usually use an aluminum blech.
The hardware store to which your reader referred simply cuts sheet metal to size and either folds over or smooths out the rough edges.