Just curios to know if others that tow a lot, notice when you are backing up to hook up, and you get that ball perfectly lined up under the hitch, and you put it in park, the truck rolls forward sever...
Yes, parking brake is necessary for locking in the drive train for non movement of the vehicle when hitching or unhitching. There is about 1/2 inch tolerance for the ball and latch.
Forgot to mention, always chock trailer wheels before Un coupling the hitch. It usually jumps.