R. Idi citing R. Yirmiyah: The Halachah of a get mekushar is that he writes the name of the lender, the borrower, the names of the witnesses and the date. He ties it and then writes the same again underneath.

Question: Isn't there a concern that a person might insert any text that he wishes at the end of the document (since the witnesses only sign on the outside and do not need to read the inside of the document before they do so)?

Answer (Rav Huna): The witnesses must read it first and declare this in writing when they sign.

R. Ba citing R. Yirmiyah: The witnesses should not sign two (or more) lines away from the text (in order not to give space for additions). (Note: The Pnei Moshe adjusted the text, as stated.)

R. Idi citing R. Yirmiyah: The witnesses of a get mekushar sign along its length.

The witnesses of a get pashut sign across its width (underneath the text) on the inside, whereas for a get mekushar, they sign on the outside.

Question (R. Mana): How do the witnesses sign on a get mekushar?

Answer (Rav Huna): Between one knot and the next.

R. Idi: (In a get pashut) it is valid as long as there is not a space of two lines between the witnesses and the document

Shimon bar Vava citing R. Yochanan: Even if he wrote an unrelated text in the two line space between the witnesses and the document, it is still invalid.

Support (R. Shmuel bar Rav Yitzchak from a Mishnah in Gitin): (Concerning two documents written in parallel) If one witness signed (the right document) in Hebrew (right to left) and underneath it, another one signed (the left document) in Greek (left to right), it is pasul. (Since their signatures include their fathers' names, whose names will continue into the area underneath the other document to which they are not signing, the upper one's father's name is a break that cuts in between the document and the lower signature, and it is pasul).