A circular
korah must have a circumference of at least three
tefachim. A
korah that is at least four
tefachim wide does not need to be strong enough to support a brick (see above). The reason for this is that a
korah that it is four
tefahim wide is noticeable even if it is not overly sturdy. Many
Rishonim say that the pegs in the wall that support the
korah must also be strong enough to support the
korah and the brick.
[
שו"ע שסג, יז-יט, משנ"ב סא-סב, שעה"צ מד, וביה"ל ד"ה חזקה; וראה משנ"ב ס; ביאורים ומוספים דרשו50,]