|This article covers how to add or remove the shim behind the latch so the door is secure when shut.|
|The shim is a spacer between the cab and the latch.|
Look at the latch. There are two phillips head screws and a bolt which is 5/16. Remove them and the shim/spacer is behind. There will one or two.
If the door does not close tightly remove one of the shims and put it back together. If it's hard to close the door add another shim.
Line up the shim with the latch and screw it back on.
Close the door and you should feel a notable difference when the door is shut.