Halakhah for Menachot 51:20

And he should be careful (Mishneh Torah, Laws of Tefillin, Mezuzah and the Torah Scroll 7:8-9) about the big letters and the small letters, the dotted letters and the letters the form of which is unusual, such as the bent [letter] peh, and the twisted letters — like the scribes copied, one man from another. And he should be careful with the crowns and in their numbers — there is a letter that has one crown upon it and there is [another] letter that has seven upon it. And all of the crowns are like the form of a [letter] zayin, [that] are as thin as a strand of hair. And all of these things are only said for an ideal [fulfillment of the] commandment. And [so] if he diverged [erred] in this refinement or was not exacting with the crowns, but he wrote all the letters as fits them; or if he made the lines closer or further or lengthened them or shortened them — since he did not have one letter cling to [another] letter and he did not miss or add or destroy the form of [a single] letter, and he did not make a change in the open paragraphs (petuchot) or in the closed paragraphs (setumot), behold this is a fit Torah scroll. [These] and the rest of the details of the commandment are elucidated in Tractate Menachot [in] the third chapter, and in the first chapter of Bava Batra and in Tractate Shabbat.