Reference for Menachot 63:3

לא אריוח וכמה ריוח אמר רב מנשיא בר יעקב ואמרי לה אמר רב שמואל בר יעקב כמלא אטבא דסיפרי

Now presumably [the halachah referred to the ruling] of leaving [the space between] the sections open? - No, it referred to the ruling of leaving a space [above and below]. And how much space must there be? - R'Menashya B'Jacob (others say: R'Samuel B'Jacob) said, The space taken up by the clasps of the scribes.<span class="x" onmousemove="('comment',' Clasps were used by scribes to prevent the sheets of parchment from rolling up.');">³</span>

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