Study Guide Eruvin 12 Today's daf is dedicated by David Freudenstein in honor of Dr. Anna Urowitz-Freudenstein - "From your loving husband and children, on the occasion of your upcoming birthday, and in appreciation of the Simcha Shel Mitzva of learning and teaching Torah which you bring to all of us and to your many students."  Rabbi Eliezer requires 2 posts - does that also include a crossbeam? How does one allow carrying in a courtyard if the wall is breached? Does one need one board or two? Is there a minimum measurement required for the board? Is there a difference between a post and a beam in terms of the way they "correct" an alley - does the post "create" a wall and a beam is a noticeable marker? Is an alley whose width is equal to (or greater than) its length treated like a courtyard?