Putting your bikes in the back of your truck used to mean throwing them in the back and praying they didn't grind against each other through the paint of both the bed and each other's frame.
The good news is that most rack guys cycle, including the ones who design this stuff. Securing your bike in the back of a truck bed is a great way to carry them. They're more out of the windstream, protected from bugs and rock chips, and they are lower and easier to handle as you can just stand in the bed and walk them in. If you have a top(per)less truck, you'll find your solutions here.