Yosef Karo

“ Shulchan Aruch Orach Chaim 691 The laws concerning the writing and the sewing of a Megilah scroll
דיני כתיבת המגילה ותפירתה
691:1 A megillah can only be written with ink on whole-hide leather or outer-skin parchment like a Torah scroll. If it is written with gall-oak fluid or caper fluid it is kosher. If it is written with pigments of other colors, it is invalid. It needs ruled lines like a Torah. The hide does not need to be tanned for the purpose [of making a megillah] . Some say that it does require purposeful tanning. ”

“ Because there are different interpretations [of the Talmud on this legal subject] , in order to fulfill the obligation according to all of them, one should make three stitches at the top, three at the bottom, three in the middle, one stitch in the fourth portion on one side and one stitch in the fourth portion on the other side. Rem"a: If there is no more sinew, it is better to sew the rest of it with flax thread than to leave it unattached (Hagahot Maimoni ch. 2 and Kol Bo) . However, if there is sinew, one should sew the whole megillah with sinew. ”