On (it appears) British aircraft some of the flying wires are cable. The really shiny ones are actually airfoil shaped rods that are being used and not cable.
If you look at the photo just above in Paddy's post, the bottom most "cable" is a real cable. The other 3 items are the airfoil shaped rods. Those don't actually do turnbuckles, but the ends thread on with a jam nut.
I think that the British were the only ones that actually did this while the German's, French, and Italian aircraft were all cables.
Also turnbuckles were only used on one end of a cable. In the photos I have looked at the turnbuckles are always placed at the most accessible end. For example, where a cable attaches to a bottom wing, or the easiest to reach. The rods were usually a pre set length with the ends threaded and both ends were adjustable and looked as in the photo above.
Here are a couple of photos of the Sopwith Camel at the Air Force Museum showing the ends of the rod mountings.
Here are some from a Spad
A Caproni bomber
And a German Halberstadt
Also it seems that American planes (Curtiss Jenny) had the airfoil rod set up as well.