When you think of a knife with a ring in the handle butt, a karambit probably comes to mind. Fact is, there are other knives with such a feature. In fact, some have rings at the middle and also even at the front of the handle.
Unlike karambits, in which the ring is used for quickly spinning the knife in between different grips as well as affecting the grips themselves, non-karambit versions of such knives employ the ring in utilitarian ways that are less flashy.
Examples include assisting in providing a more secure purchase on the handle, dangling the knife from a pinky to allow for full use of the hand while keeping the knife handy, attaching the knife to a keyring, or simply hanging the knife on a tool rack or elsewhere.
If your approach involves frequent intermittent knife use, interspersing it with employing your hand to grip, hold or pull the material you’re cutting or some other method all your own, then adding a ring knife to your collection might be beneficial.