A turnbuckle, rigging screw and bottlescrew are devices used in the tensioning of wire ropes, cables, tie rods and other tensioning systems.
The main difference is the body of the fitting.
What is a turnbuckle?
Turnbuckles have an open body, exposing the threaded section. Often used in shade sails and marine applications.
What is a Bottlescrew?
Bottlescrews have an enclosed body, hiding the threaded section. Often used in wire balustrade systems but also in shade sails and marine applications as well.
In additional to the screw bodies there are a few other points of difference.
