A turnbuckle is an adjustable end termination for the ends of cables, wires, rods, or sometimes even rope. Typically consisting of a threaded body and stud, they are particularly useful for achieving the proper amount of tension on permanent or semi-permanent structures and load bearing rigging.
Most turnbuckles are relatively long and narrow – a longer turnbuckle would inherently provide a longer range of adjustment for tensioning or lengthening. Many turnbuckle bodies have opposite threads (RH/LH) on either end so that when the turnbuckle is turned one way both ends will tighten, and tension will increase. When turned the opposite way, both ends will loosen, and the tension will decrease. Other turnbuckles only have one threaded end for adjustments and the other end will have some form of connection like a fork or toggle.
Turnbuckles are used in countless engineering, rigging, or construction projects that require either structural or aesthetic cables or rods. One of the advantages of a turnbuckle is that adjustments in tension can be done in tiny increments to achieve the precise tension required, often calculated by an engineer.