A turnbuckle is a device for adjusting the tension in ropes, cables, and tie rods. It normally consists of two threaded eyelets, one screwed into each end of a small metal loop, one with a left-hand thread and the other with a right-hand thread. The tension can be adjusted by rotating the loop, which causes both eyelets to be screwed in (or out). Turnbuckles are most commonly used in applications which require a great deal of tension; they can range in mass from about ten grams for a small cable to tens of kilograms for structural elements in buildings and suspension bridges.
