Binding fiber, (raiment); stout twine made of strips of leather or of a fiber like hemp; a piece long enough to circle a slave girl's waist 2-3 times is often used as a belt for her slave tunic.

"Your wrists were bound together before you," she said, "and a doubled rope put through them. When you were within our reach, and we could hold you, the other end of the rope was dropped, and it was then withdrawn. We removed your bonds,"
"Of what nature was the bond?" I asked.
"Binding fiber," said Tupita
Book 22, Dancer of Gor: Page 374
The saddle pack contained the light gear carried by raiding tarnsmen -- in particular, rations, a compass, maps, binding fiber, and extra bowstrings.
Book 1 of Gor: Tarnsman of Gor, page 64
Instead I felt binding fiber cinched about my waist, and then my hands, wrists crossed, were, to this same fiber, tied behind my back.
Book 22, Dancer of Gor: Page 375
However, the camisks that I have personally seen, and those we were given, were belted with a long, thin strap of leather binding fiber. This passes once around the body, and then again, and then is tied, snugly, over the right hip.... The belt ofbinding fiber not only makes it easier to adjust the camisk to a given girl, but of course, the binding fiber serves to remind her that she is in bondage.
Book 7, Captive of Gor: Page 64