your fingers a gap of about half a finger’s breadth (1), the grip is sound; if it is any wider or narrower, it serves no good purpose.

On the hook and its varieties
(2) Archers speak of nine ways of hooking the string:

1. The first—and it is the sound, excellent, and powerful method—is the sixty-three hook.
2. The second is the sixty-nine hook. These two hooks are used by all the Sāsānids and Khosrows, though they consider the first the more correct and dependable.
3. The third is the seventy-three hook.
4. The fourth is the eighty-three hook.
5. The fifth is the twenty-four hook.
6. The sixth is the twenty-one hook. Most of the Turks and Byzantines employ this because they shoot with a supple bow that lacks a firm core, so they hook the string in whatever way proves easiest for them.
7. The seventh is a hook called al-radīf: it is a possible sixty-two hook in which the middle finger is placed together with the index on top of the thumb. This hook is good for drawing a stiff bow, but it releases slowly.