Here are relevant references from the Books where a strap as a whip is mentioned.
I make no pronouncements on these matters, but report them as I find them.
Arrive at your own conclusions.
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A guard is not used in such cases to prevent the escape of the girl, for, in such a situation, in a house or Kasbah, there is escape for her. He serves to protect her, interestingly, from other slave girls. The strap or coiled rope he carries is used less often to hasten, in a humiliating fashion, a girl who might otherwise dally on the way to discipline, though it may serve this purpose, than it is to drive other girls from her. Such a strap or rope, of course, can sting hotly through slave silk. She is very vulnerable, you see, the girl who is to be punished, on the way to discipline. She is naked; she is not permitted to rise; she may not even speak, for the whip must be held between her teeth; to drop it is twenty extra lashes. Resentments, jealousies, petty feuds, enmities, are common among female slaves. Particularly is there jealousy and hatred for the most beautiful slaves, or for the highest slaves. Such a girl, on her way to discipline, is a delight to those who hate and envy her, and who would be only too pleased to take this opportunity to jeer and abuse her, sometimes cruelly and physically. Although many girls in the kasbah were chained here and there for the pleasures of men, most were freed of impediments, that they might fetch and serve, and be seized when and wherever the men might want them. These, in the halls, would constitute a genuine danger to Vella, who, a high slave, had been the object of much envy. How pleased they would be to see proud Vella crawling in the halls to her discipline. The second reason a man accompanies the girl is to be the caller. He performs what is spoken of sometimes as the whip song, though it is not a song, but rather a series of calls or announcements. These summon other girls to witness one of their sisters on the way to discipline. "Here is a girl who has not been fully pleasing," cries the man. "Look upon her. She is going to discipline. She was not completely pleasing. See her! Come, witness a girl who has not been fully pleasing!" These cries bring the other girls, with their burdens, and such, to watch the progress through the halls of the girl who is to be punished. Soon a derisive, moving gauntlet is formed, through which, constantly, the miserable, whip-bearing girl crawls. She is spat upon, and struck, with hands and straps, and kicked, and much abused, but, of course, only within those limits set by the caller and guard. This sort of thing is thought desirable in the Tahari, in encouraging the whip-bearing girl to be more dutiful in the future, and the girls of the gauntlet to resolve, too, to be more dutiful, that it not be they, next, at the mercy of their enemies and rivals, who carries the whip. The actual whipping in the Tahari, incidentally, is usually a matter between the girl and the master, or he and his men. Other girls are seldom permitted to watch one of their sisters being whipped. All they know, when the doors close, is that she will be whipped.