• Acc. to Rav Yirmiyah bar Abba, עדים sign from the bottom of the שטר, running upwards

On the previous Daf, Rav Yirmiyah bar Abba taught that עדים sign on the back of a גט מקושר, opposite the text on the front. The Gemara assumes they sign one above the other, in the same direction as the text in front. Therefore, Rami bar Chama asked Rav Chisda that we should be concerned that the person holding the שטר will write whatever he wants at the end of the text inside the שטר, and sign forged signatures on the outside of the שטר parallel to his added text, and claim: אנא לרבות בעדים הוא דעבדי – “I did this to increase the number of עדים in the שטר, to fully publicize the transaction.” The שטר can be certified with any two signatures, without certifying his fraudulent signatures!? Rav Chisda answered that according to Rav Yirmiyah bar Abba, the עדים do not sign parallel to the text in front. Rather, עדים ממטה למעלה חתימי – the witnesses sign from the bottom to the top, perpendicular to the text. Since their signatures begin opposite the end of the text, it cannot be added to.

• The concern he will cut off a harmful clause from the last line, leaving part of the signature

The Gemara asks that perhaps there will be a clause in the last line which is harmful to the holder of the שטר, and he will cut it off. Although he will likewise cut off the “Reuven,” the first name of the עד signed behind that line, ומתכשר בבן יעקב עד – it will still be valid with the remaining signature, which states “ben Yaakov, witness,” because such a signature is valid!? The Gemara answers that “Reuven ben” are written opposite one line of text, and both will be removed if he cuts off a line, leaving him with only "יעקב עד". The Gemara asks that perhaps it will still be validated, based on the assumption that “Yaakov” signed the שטר. It answers either that "עד" is not written (and “יעקב” alone is not a valid signature), or it is recognized that this is not the signature of anyone named Yaakov.

• There is no concern that a son signs using his father’s name, even as a symbol

The Gemara continues to challenge the answer that the שטר’s holder cannot cut off the last line, because he will only be left with "יעקב עד". ודלמא בשמיה דאבוה חתם – Perhaps [Reuven] signed using his father’s name (as a sign of respect), and it will authenticated with "יעקב עד", since it is Reuven’s handwriting!? The Gemara answers: לא שביק איניש שמיה דידיה וחתים בשמיה דאבוה – a person does not leave his own name and sign using his father’s name. The Gemara persists that perhaps he uses his father’s name as a symbol for signing, as we find that Amoraim signed various symbols in place of a signature (for example, Rav would draw a fish)!? The Gemara answers: לא חציף אינש לשוויה לשמיה דאבוה סימנא – a person is not so impudent as to make his father’s name a symbol.

Mar Zutra answers that the entire issue is resolved easily, because כל מקושר שאין עדיו כלין בשיטה אחת פסול – any שטר מקושר whose witnesses do not all conclude on the same line is invalid. Since their signatures all begin (or end) opposite the last line of text, cutting part of any signature would cut all of them, and his fraud would be discovered.

Siman – כסא Chair. The עדים signing on a גט מקושר lying flat on a massive chair were instructed to sign from the bottom up starting at the end of the text, and not to worry about anyone cutting off the bottom because no one in town named Yaakov signs like that, and no one would use their father's name, because if he wouldn’t sit in his chair he certainly wouldn’t use his name.