Tailgate adjustment for gaps

Can anyone tell me how to adjust the side to side gaps on the tailgate? The left side is dang near a half inch and the right side is almost touching. So I need to slide it to the left about a quarter inch to even it out. I can't figure out how to do that though.

 

Sometimes you can just open the tailgate, and slide it the direction you need. There should be a small amount of play available. If you have a topper with a lot of weight on the bed rails, it's also possible your bed is spreading, which is why a lot of us run bed stiffeners.

 

Nothing on top and I have bed stiffeners.

 

Open the gate 45 degree's or so, wiggle it back over to taste, close the gate, done.