Quickly review the גמרא דף י: “וליחוש (seventeen lines from top of the Amud) until “תנן התם”
The Gemara discusses a case where the fourth side of the Mavui is 15 Amos wide and places a board 3 Amos wide leaving a gap of space of 2 Amos between the board and the wall.
Questions:
What is the problem if the people stop traveling through the larger opening and only go through the smaller opening?
Rashi says one reason
See ח’ מאירי “וליחוש who says a different reason.
Does one need to place a Lechi or Korah for the gap of 2 Amos?
Learn חידושי מאירי beginning of of דף י עמוד ב who quotes the Raavad
Does one need to place a Lechi or Korah in addition to the פס for the opening of 10 Amos?
See “תוס’ “ועושה who says he needs a Lechi or Korah
Why does the Lechi need to be within three tefachim of the wall?
See רבינו יהונתן דף יד: על המשנה “ר’ יוסי
https://hebrewbooks.org/pdfpager.aspx?req=14312&st=&pgnum=332
Learn מגן אברהם ס’ שס”ג ס”ק ה who explains there is a dispute between Tosfos and רבינו יהונתן?
https://hebrewbooks.org/pdfpager.aspx?req=14325&st=&pgnum=231
In the case where the entrance to the Mavui is 20 Amos wide and places a board four Amos long in the middle of the entrance in the direction of the side walls.
Does one need to place a Lechi or Korah on only one of the openings or on both?
See רש”י דף ה. “מתיר בפרצה
The gemara says we are not concerned that people will abandon the larger opening for the smaller opening unless there is a gain of a shortcut.
What happens if the people actually do abandon the larger opening?
See שולחן ארוך או”ח ס’ שס””ג סע’ לד and משנה ברורה ס”ק נ