A turnbuckle, stretching screw or bottle-screw is a device for adjusting the tension or length of ropes, cables, tie rods, and other tensioning systems. It normally consists of two threaded eye bolts, one screwed into each end of a small metal frame, one with a left-hand thread and the other with a right-hand thread.
Stainless Steel Turnbuckles can tension assemblies without twisting them up because one end fitting is left hand threaded and the other is right hand threaded.