Reference for Menachot 60:1

אלא שלש בתוך הדף ושתים חוץ לדף נזדמנה לו תיבה בת שתי אותיות לא יזרקנה לבין הדפין אלא חוזר וכותב בתחילת השיטה

but three in the column and two outside.<span class="x" onmousemove="('comment',' If therefore there is sufficient space for three letters he may write the word allowing two letters to encroach upon the margin; but if there is not sufficient space for three letters he must write the whole word in the next line.');">¹</span> If [when he has come to the end of the line] he has to 'write a word of two letters, he may not insert it between the columns but must write the word at the beginning of the next line.

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