Turnbuckle
From MITNA
A turnbuckle is a device for adjusting the tension or length of lines or cables.
It consists of two threaded rods, one screwed into each end of a metal frame, one with a left-hand thread and the other with a right-hand thread. Turning the frame one direction or another serves to tighten or loosen the lines.
Shrouds and stays are usually attached to a boat at the bottom with a turnbuckle to allow them to be tightened.
