How to back a semi truck?

Stop the truck, shift into reverse, let off the clutch. Or, if you have an automatic, you just push the button for reverse, then take your foot off the brake. As for maneuvering a trailer, turn the wheel to the left to turn the trailer right and vice versa. If you get a diecast model of a semi truck and trailer and maneuver the trailer while you back it up, it could give you a basic understanding of how it works.