Qur'anic Studies: Meaning of the word "tooth" [closed]

In the meantime, Luxenberg has made two proposals that relate to the question of how the text was first written. First, he argues that the “Ur-Qur’an” sometimes used a single “tooth” as mater lectionis not (or not only) for long i, as it does today, but to indicate long a, rather than the alif that later was introduced to mark it; but knowledge of this early convention was subsequently lost, so that the “tooth” was then mistakenly pointed to represent y, t, or another letter that the “tooth” could represent.

Solution 1:

Arabic script contains many markings and letter variations. The tooth is a basic feature of the script. Its form varies, which partly explains why the quotation deals with it in such detail.

Creative Arabic Calligraphy "The most basic shape is a vertical stroke (in essence, not necessarily in form), a tooth that can be thought of as the Alif shortened" {Note that Alif is a very common letter consisting of an almost upright stroke}.