Putting on a blech on Shabbat

Hi,

One who forgot to put the blech on a flame before Shabbat may put it in place on Shabbat, if the flame is so low that it will not heat up the blech to the point of making it like a coal. Heating the blech in this way would be an act of quasi-cooking, according to some authorities. If the flame is that high, one should not do this, other than in case of need.

(Rivivot Ephraim 1:185)

Have a great day,
Mordechai