Bava Batra 163: Sneaky Document Forgeries

The rabbis continue to debate the end of a valid document.  They have determined that a forgery or another addition could be written on two extra lines of a document after it has been signed.  Thus a document is invalidated if there are two or more lines left blank at the end of a document.  So how must a document end?  How must a document be signed?  

Amud (a) has the rabbis considering how many blank lines would be required, in fact, to add invalid additions to the document.  Do we count the space between the two lines as well?  Certain letters extend above a line and others drop below the line.  A scribe would never stoop to invalidate a document by writing additional text, and thus an addition would be written by a non-professional.  Would they know or notice how the letters should appear?  Wouldn't it be easy to spot a forgery?

Next we are privy to the rabbis' debates regarding where we are permitted to leave space in a document.  We know it is not acceptable to leave space between the text and the witnesses.  What about leaving space between the witnesses and the Beit Din's validation of the document? Some rabbis believe that there should be no space at all.  Others believe that a space between the witnesses and the validation of the Beit Din is permitted as long as there is a smudge of ink present to demonstrate that it is not a space to be used.  There is much argument about this last point.

Amud (b) moves into even more bizarre suggestions of forgery.  It is suggested that even one blank line between the witnesses and the validation should disqualify the document.  This is because there are one-line documents.  A forger could cut off the top of a document, write a one-line statement, and claim that the document has been validated by the court.  And might such a person even forge the signatures of witnesses?  Should there be no blank space at all in a valid document?