Question (Rav Nachman): Why don't we learn from the last line of a document?

Answer (Rav Amram - Beraisa #1): If the witnesses left two blank lines between the text and their signatures, it is invalid; if they left one blank line, it is valid.

Question: When they left two blank lines, it is invalid. Presumably, we are concerned lest the bearer add clauses to his benefit;

The same concern applies when one blank line was left!

Answer: We must say that we do not learn from the last line.

Question: If one and a half blank lines were left after the text, what is the law?

Answer #1 (Beraisa #1): If they left two blank lines, it is invalid.

Inference: If they left one and a half blank lines, it is valid!

Objection: The Seifa teaches that if they left one blank line, it is valid. This implies that if they left one and a half blank lines, it is invalid!

Conclusion: The inferences contradict one another. We cannot determine which is correct (to answer the question from the Beraisa).

Answer #2 (Beraisa #2): If they left two blank lines, it is invalid. If they left less than this, it is valid. (This answers our question. The Gemara brings the entire Beraisa.)

If four or five witnesses signed on a document, and one (our text, Rambam; Rashbam's text - the first two) of them were found to be relatives or invalid witnesses, the document is valid due to the Kosher witnesses.

This supports Chizkiyah.

(Chizkiyah): If blank lines between the text and the signatures were filled with signatures of relatives, it is valid;

We likewise find in the laws of Sechach (that a gap is worse than something invalid). Three Tefachim (width) of air (from one end of the Sukah to the other) disqualify a Sukah, but invalid Sechach disqualifies a Sukah only if it is four Tefachim.