Learn the גמרא דף ח. “ההוא מבוי עקום (middle of the Amud) until the next set of two dots.
Continue learning the Gemara until דף ח: “איתמר (five lines from top of the Amud)
Last week we learnt the גמרא דף ח. “מרימר פסיק לה לסורא באוזלי. Rashi learnt מרימר placed the nets on the end of the street before the sea. However the מגיד משנה explained according to the Rambam who rules we are not concerned for שמא יעלה הים שרטון the case was that מרימר placed the nets on the other open side of the street.
Question on the מגיד משנה:
Rabbi Jaffe asked me the following question on Shabbos.
What was the need to place nets – a full wall on the fourth side as since the sea wall is a valid wall than this road is a classic dead end mavui which only requires a Lechi or Korah on the fourth side?
For a novel explanation see בית מאיר ס’ שס”ג סע’ כט