אבן העזר קכ״דEven HaEzer 124

Se’if 1א׳

גֵּט שֶׁכְּתָבוֹ עַל אִסוּרֵי הֲנָאָה, כָּשֵׁר. מִיהוּ, בְּדָבָר שֶׁצָּרִיךְ בִּעוּר מִן הָעוֹלָם וְצָרִיךְ שְׂרֵפָה, אִם כָּתַב עָלָיו הַגֵּט, בָּטֵל (הָרַ"ן פֶּרֶק בָּתְרָא דְּגִטִּין):

A divorce document that is written on something that it is prohibited to get benefit from is valid. Rem"a: However, if it is something that requires being removed from the world and needs to be burned, and he wrote the divorce document on it, the document is nullified. (Ran Gittin)

Se’if 2ב׳

כּוֹתְבִין הַגֵּט עַל דָּבָר שֶׁיָּכוֹל לְהִזְדַּיֵּף, וְהוּא שֶׁיִּתְּנֶנּוּ לָהּ בְּעֵידֵי מְסִירָה. כֵּיצַד, כּוֹתֵב עַל הַנְּיָר הַמָּחוּק וְעַל הַדִּפְתְּרָא וְעַל הַחֶרֶס וְעַל הֶעָלִין וְעַל יַד הָעֶבֶד וְעַל קֶרֶן הַפָּרָה, וּמוֹסֵר לָהּ הָעֶבֶד וְהַפָּרָה אוֹ שְׁאָר דְּבָרִים בִּפְנֵי עֵדִים. אֲבָל לֹא יַחְתֹּךְ יַד הָעֶבֶד וְקֶרֶן הַפָּרָה וְיִתֵּן לָהּ, וְאִם כָּתַב [וְחָתַךְ] וְנָתַן לָהּ, אֵינוֹ גֵּט, מִשּׁוּם דְּבָעֵינָן שֶׁלֹּא תְּהֵא קְצִיצָה בֵּין כְּתִיבָה לִנְתִינָה. הַגָּה: וְכוֹתְבִין עַל כָּל דָּבָר תָּלוּשׁ (טוּר) וְיֵשׁ אוֹמְרִים דַּוְקָא בְּדָבָר שֶׁהוּא שֶׁל קְיָמָא, אֲבָל אִם כָּתַב בְּעָלֶה שֶׁל בְּצָלִים אוֹ יְרָקוֹת וְכַדּוֹמֶה לָזֶה, פָּסוּל (הָרַ"ן פֶּרֶק שֵׁנִי). וּלְכַתְּחִלָּה יֵשׁ לְכָתְבוֹ עַל קְלָף מְתֻקָּן לְסֵפֶר תּוֹרָה תְּפִלִּין וּמְזוּזוֹת, אֲבָל לֹא בָּעִינָן מְעֻבָּד לִשְׁמוֹ; אֲבָל אֵין עִכּוּב בְּדָבָר זֶה (מ"כ בְּסֵדֶר גִּטִּין) וַאֲפִלּוּ אִם נִכְתַּב עַל נְיָר שֶׁקּוֹרִין פַּפִּי"ר, בְּכָל כְּתָב, כָּשֵׁר (גַּם זֶה שָׁם). וְעַיֵּן לְקַמָּן רֵישׁ סִימָן קכ"ו:

Gets [bills of divorce] are written on objects which can be falsified [as long as] it is given with those who witness its delivery. For example, he writes it on paper which has been previously erased, and on animal hide, and on ceramic, and on leaves, and on the hand of a slave, and on the horn of a cow -- and he delivers to her the slave or the cow or other objects in the presence of witnesses. But he should not cut off the slave's hand or the cow's horn and give it to her. And if he wrote it [on the hand or horn] and cut it off [to deliver] to her, it is not a valid bill of divorce, because it is a requirement that the object is not cut between the time of writing and the time of giving it. "Rem"a:" it can be written on any object which is separated from the ground, and there are those who say, only on an object which will endure. But if he wrote it on the leaf of an onion or vegetables or similar items, it is invalid (Ran, Chapter 2). The optimal way is to write it on parchment [from animal hide] which is prepared [in the same manner as] a Sefer Torah [Torah Scroll], Tefillin [Phylacteries], and Mezuzot [Doorway Scrolls] -- however it is not required that [the parchment] be processed specifically with the intent for use for a Get. However [not using this type of parchment] does not prevent the Get's [validity], even if it is written on the type of paper called "paper" [i.e. paper from wood pulp], [it can be written with] any type of writing, and is kosher [valid]. Also, refer ahead to at the beginning of Siman 126.

Se’if 3ג׳

טוֹב לַחְתֹּךְ הַנְּיָר לְמִדַּת הַגֵּט, שֶׁלֹּא יִצְטָרֵךְ לַחְתֹּךְ מִמֶּנּוּ אַחַר כְּתִיבָה. וְאִם טָעָה הַסוֹפֵר לְאַחַר שֶׁכָּתַב קְצָתוֹ וְרוֹצֶה לְהַתְחִיל בְּאוֹתוֹ נְיָר עַצְמוֹ, יַחְתֹּךְ תְּחִלָּה הַמּוּעָט שֶׁכָּתַב. הַגָּה: אִם כְּתָבוֹ עַל נְיָר גָּדוֹל, וַחֲתָכוֹ לְאַחַר הַכְּתִיבָה קֹדֶם הַנְּתִינָה, פָּסוּל. אֲבָל אִם חָתַךְ מִמֶּנּוּ מְעָט, כְּדֵי לְיַפּוֹתוֹ, לָא מִקְּרֵי קְצִיצָה (טוּר בְּשֵׁם הָרֹא"שׁ). וְכָל שֶׁלֹּא חָתַךְ מִמֶּנּוּ הַרְבֵּה יוֹתֵר מִכְּתִיבַת הַגֵּט, הָוֵי כִּלְיַפּוֹתוֹ (כֵּן מַשְׁמַע בְּסה"ת). אֲבָל לְכַתְּחִלָּה חוֹתְכִין מִמֶּנּוּ הַכֹּל קֹדֶם הַכְּתִיבָה, אֲפִלּוּ הַנְּקָבִים שֶׁעוֹשִׂין כְּדֵי לְשַׂרְטֵט עַל יָדָן, וּשְׁאָר הַדְּבָרִים, יַחְתֹּךְ הַכֹּל קֹדֶם הַשִּׂרְטוּט, דְּהַשִּׂרְטוּט צֹרֶךְ כְּתִיבָה הוּא (סֵדֶר גִּטִּין). כְּתָבוֹ עַל סֵפֶר, אַף עַל פִּי שֶׁיֵּשׁ בּוֹ עִנְיָנִים אֲחֵרִים, וְנָתַן לָהּ הַכֹּל, כָּשֵׁר (טוּר בְּשֵׁם הָעִטּוּר):

It is good to cut the paper to the measure of the get, so that he will not need to cut it after writing, and if the scribe erred after he wrote a little bit of it and wants to start on that paper itself, he should first cut the little bit that he wrote. Hagah: If he wrote it on a large paper, and cut it after writing and before it was given, it is invalid. But if he cut a little from it, in order to beautify it, it is not called cutting (Tur in the name of the Rosh). And as long as he has not cut from it much more than the [space used in] writing the get, it is considered beautifying it (thus is implied in the case of a Torah scroll). But preferably they do all cutting from it before the writing, even the indentations they make in order to score it, and the other things, and he should do all the cut before the scoring, for the scoring is needed for writing (Seder Gittin). If he wrote it in a book, even though there are other matters in it, and gave it all to her, it is valid (Tur in the name of the Itur).