What are turnbuckles used for?
Also, can turnbuckles be used for lifting?
Rigging screws / turnbuckles are also used for lifting applications though before using to lift with please check with the operation and used manual to ensure that they are certified for lifting; the reason being that many manufacturers only certify for pulling applications.
In respect to this, how do you stop turnbuckles from turning?
Tighten until your rigging assembly is tensioned to the desired point needed for your application. If your application will expose the turnbuckle to vibration, it is good practice to lock the end fittings from turning by using lock wire. This will prevent unwanted loosening over time.
Turnbuckle assemblies are used with control cables to provide desired cable tension. They are made in a range of sizes and in both long "L" and short "S" assemblies.