A THUMB-TIP—which is called kustubān by the Persian and khayta‘ah by the Arabs—consists of a ring or leather or some other material. It is worn over the right thumb, leaving the nail and knuckle exposed, and is use for the protection of the thumb against injuries which are usually caused by the string when it is drawn and release (Its use is necessary except when the archer employs a very weak bow for executing some stunt or for shooting at near target. Shooting without a thumb-tip, whenever possible, is better and offers greater accuracy. For this reason [to resemble the bare skin], a thumbtip should be mad of leather that is even in texture and moderate in thickness, and should be lined with very fine leather and sew with great care. An almost invisible groove should be mad in it for the string. The end which lies on the tip of the thumb should be fashioned like a small, broad bean of moderate thickness; not so long as to impede the string, so short as to fail to protect the thumb from the action c the string. In width it should be the same as the thumb itself, with its back part a little narrower than its front part. The side of the leather that is smoothed in the tarning should be next to the string.
Thumb-tips are often made of the skin of horses or goats, or of other kinds of tanned hides, as well as of silver, copper, iron, bone and horn. The last variety is made b taking a fine horn, large enough to hold the thumb, an cutting it down to the right size; then a piece is carved out to expose the nail and the knuckle of the thumb, and groove for the string is marked on the face of it. The same process is followed in making tips of silver or other metals.
The best thumb-tips, however, are made of leather of moderate thickness, neither too thick lest they interfere with the efficiency of shooting, nor too thin lest they fail to protect the thumb against the action of the string.
Leather tips are superior to those of silver and the other metals because they are soft and flexible and interfere least with the accuracy of shooting. Some archers, however, hold that tips of silver or of other metals are better than tips of leather in competitive and distance shooting. Ṭāhir al-Balkhi said that for distance shooting thick tips are better, while for accurate target shooting thin tips are superior. This is, in fact, correct.