A number of the laws distinguish specifically between the way a Torah must be written and the way a mezuza is written. For example, certain parts of the Torah, like Parashat Ha’azinu and Shirat HaYam – the song sung by the Children of Israel upon crossing the Red Sea – are written as song or poetry. These special songs must be written in a unique fashion, and the rest of the Torah cannot be written in that way, while a mezuza can be written in poetic form, even though that is not the ordinary way of writing it. Another example is the length of a given line. A line in the Torah must have at least 30 letters in the line (the word lemishpeḥoteikhem written out three times), while a mezuza may have even two words on a given line.
There is, of course, a single tradition regarding how the two parshiyot, or chapters, of Shema and ve-haya im shamo’a in mezuzot are to be written, which has been the practice of Jewish scribes for hundreds of years. This standard model has 22 lines, each of which opens with a specific word. According to this ancient tradition, the second parasha – ve-haya im shamo’a – starts at the beginning of the seventh line. This does not allow for the usual split between two separate parshiyot, which ordinarily is an empty space dividing between the conclusion of the first parasha and the beginning of the second parasha on the same line. This is resolved by following the position of the Rambam so that an empty space is left following the end of the first parasha, and the second parasha – ve-haya im shamo’a – is indented into the following line.