Sukkah 15B

והא אפשר לצמצם! אמר רבי אמי: במעדיף.

The Talmud asks: But isn’t it possible to be precise? The Mishnah need not be understood in that manner, since it is possible to calibrate the width of the spaces to equal the width of the unfit roofing, as the Mishnah required no more than that. R' Ami said: The Mishnah is referring to a case where one extends the width of the spaces beyond the width of the unfit roofing. The Mishnah deems the sukka fit only if the width of the spaces is greater than the width of the unfit roofing.

רבא אמר: אפילו תימא בשאין מעדיף, אם היו נתונים שתי ⁠— נותנן ערב, ערב ⁠— נותנן שתי.

Rava said: Even if you say that the Mishnah is referring to a case where one does not extend the width of the spaces, and nevertheless, the fit roofing is greater than the unfit roofing, if the skewers were placed lengthwise across the sukka, one places the fit roofing widthwise, and if the skewers were placed widthwise, one places the fit roofing lengthwise. By doing so, the fit roofing overlaps the skewers at least somewhat; otherwise it would fall between the unfit roofing. Consequently, even if the space equals the unfit roofing, the fit roofing is greater than the unfit roofing.

או בארוכות המטה. לימא מסייע ליה לרבי אמי בר טביומי, דאמר רבי אמי בר טביומי: סככה בבלאי כלים ⁠— פסולה.

§ The Mishnah continues: Or with the long boards of the bed, which compose its frame, the sukka is unfit. The Talmud suggests: Let us say that the Mishnah supports the opinion of R' Ami bar Tavyomei, as R' Ami bar Tavyomei said: If one roofed the sukka with worn, incomplete, vessels, the sukka is unfit. Although these incomplete vessels are no longer susceptible to ritual impurity, they remain unfit because they were initially unfit for roofing. Proof can be adduced from the Mishnah: The long boards of the bed are no longer vessels but rather pieces from broken vessels; still, they may not be used for roofing the sukka.