Turnbuckle (noun)

1. A device consisting of a metal rod with screw threads at each end and a rod or pin that can be turned to adjust the tension in a rope or cable that is passed through its two ends.
2. A device for adjusting the tension in a rope, cable or chain by turning the rod to change its length.

Origin:

Mid 19th century: from turn (verb) + buckle.

Examples:

1. The turnbuckle was used to adjust the tension on the guy wire.
2. He used a turnbuckle to adjust the tension on the cables.
3. The turnbuckle is a handy device for adjusting the length of the rope.
4. The turnbuckle is designed to be adjusted with a wrench.
5. The tension was adjusted by turning the turnbuckle.