Avodah Zarah, Daf Lamed Aleph, Part 3
Introduction
The Talmud defines what is considered a seal within a seal. These are pretty self-explanatory, at least once they have been translated.
היכי דמי חותם בתוך חותם? אמר רבא אגנא דפומא דחביתא שריקא וחתימא הוי חותם בתוך חותם ואי לא לא
What, for example, is a seal within another seal? Rava said: A basin placed over the opening of a barrel and joined to the barrel with a seal on it, is a seal within another seal, otherwise it is not so;
דיקולא ומיהדק הוי חותם בתוך חותם לא מיהדק לא הוי חותם בתוך חותם
A basket fastened [over the stopper] is a seal within a seal, but if it is not fastened it is not a seal within a seal.
נוד בדיסקיא חתימת פיו למטה הוי חותם בתוך חותם פיו למעלה לא הוי חותם בתוך חותם וכי כייף פומיה לגיו וצייר וחתים הוי חותם בתוך חותם
A skin bottle within a bag with the closed opening of the skin bottle on the bottom, is a seal within a seal, but if the opening is on the top, it is not a seal within a seal; if he bends in the closed opening of the skin bottle within and then ties the bottle up again and seals it, it is considered a seal within a seal.
