Very quickly review the third “בעא מיניה אביי מרבה” (middle of the Amud) until the fourth בעא מיניה אביי (nine lines from the bottom of the Amud)
Questions:
Why is it necessary to view the תל המתלקט as carved out in order to be an acceptable דיומד? Why is it not sufficient the fact that there is an Amah of a mechitza on each side?
Why does a round pillar need to be viewed as carved out and squared in order to be an acceptable דיומד? Why does it matter that the outside face plate is round? (See שפת אמת)
There are two approaches to answer these questions
Learn חזון איש
Learn ח’ מהר”ל
Learn the fourth בעא מיניה אביי (nine lines from the bottom of the Amud) until the fifth בעא מיניה אביי on the top of דף כ
Questions:
What is the reason that חיצת קנים would not be acceptable for פסי ביראות as they are considered a bona fide wall by virtue of Lavud?
What is the reason that גודריתא דקני would not be acceptable for פסי ביראות?
Learn ריטב”א
Learn ח’ מהר”ל for an explanation