A fitting which attaches a sheet to a Horse. most commonly used to move the cockpit end of the main sheet tackle more to the windward or the leeward side of the boat. For another example, an iron ring which slides along a bowsprit so that you can attach the tack of the jib from the foredeck and then haul it outboard. A third example is a ring which travels up the mast of a lugger. The halyard is made fast to the ring and the yard of the lugsail is hooked beneath.