A ring bolt is a bolt with a captive ring on one end and threads on the other end. The ring bolt differs from the eye bolt in that in the former the ring is articulated, such that it can rotate in at least one axis, and can thus reduce bending forces on the bolt when loaded and will present the minimum obstruction when "flat".
Ring bolts are commonly used to attach cables or ropes to objects, for example securing a boat to a dock, or as a tie down point for cargo.
References
Ring bolt Wikipedia(Text) CC BY-SA