fully boxed

Let's say you are a cowboy, you wear a cowboy hat and you wear a duster, and you have a pickup. You don't want someone laughing in your face. Worse, two fellers laughing, snickering, hooting and hollering, calling you a sissy. That's why you want a bad boy that's fully boxed. Let's say you're driving through a dusty town on your way to your next country music singing gig and stop in at a local watering hole. Some fools might be laughing at you after they ask what pickup you drive. To respond, you'll want to carry some rounded metal car parts in your saddlebag. Then you slam those metal objects down on their table and tell them which one of those bad boys is fully boxed.

That will shut them up. That means you are a cowboy.