Others have said, “I conceal my nails completely (1), set the string in the thumb-joint, and cant it ever so slightly.”
Both positions are sound and commendable: keeping the string perfectly straight lends greater power to the draw, whereas a slight tilt hastens the arrow’s release.
Some archers place the string a little forward of the joint, on the fleshy pad of the thumb.
This is the best of the methods, the quickest to let go compared with the first and second, and the most consistent in driving the arrow.

Section
Veteran archers maintain that power (2), speed, and range reside in the thumb that hooks the string with the right hand and in the grip of the left; upon these two the whole question of force depends. Every finger has its own hook, just as every hand has its own grasp (3). Accordingly, whether the student archer has long fingers or short, choose for him among these techniques the one best suited to his digits, most conducive to his shooting, and least likely to harm his body.

Section
There are three ways of setting the index finger upon the thumb: