The גמרא דף יא until the two dots on דף יא עמוד ב brings the opinion of רב that a צורת הפתח can not close an opening wider than 10 Amos.
Rav Yosef understands that רב would also disqualify multiple צורת הפתח on openings less than 10 Amos if there are more openings than closures – פרוץ מרובה על העומד. The Gemara tries to prove this position but is unsuccessful.
The Gemara also attempts to bring a proof that ר’ יוחנן agrees to the opinion of רב that a צורת הפתח can not close an opening wider than 10 Amos but does not have a source.
How do we conclude l’halacha?
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Note how the Ramabam rules
Major Question:
The Rambam concludes that each situation individually a צורת הפתח is valid. However when both are combined in a case of an opening wider than 10 Amos and פרוץ מרובה על העומד than it is disqualified.
If each situation independently is valid, why is the combination deadly?
Our Gemara said the source to disqualify a צורת הפתח when there are more openings than closures – פרוץ מרובה על העומד is from the halacha of Rav who rules a צורת הפתח can not close an opening wider than 10 Amos. Since the Rambam concludes a צורת הפתח is valid on an opening wider than 10 Amos where is the source to disqualify it when there is פרוץ מרובה על העומד ?
Learn מגיד משנה for an answer
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