It might just be a forgotten leftover - but on the Chyseal map you find 2 leather belts called "rope" in one and "sash" in the other case. Both can be used and crafted with rubies and essences. Found no other use, though (CR and BL at 5).
That is why I formulated those formulas very generic, like: [Crafting 5] Boosted Apparel = Apparel + Ruby (Secrets of the Scroll IX) (+ Air, Earth, Fire, and Water Resistance. +5%(IL1) / +10%(IL2) / +15%(IL7) / +20%(IL12) / +25%(IL17).)
There are just too many exceptions and special cases to handle them all.