Werner

Whenever a potential new hire tells us he wants to put in notice, I inform him that we love hearing that, but if his current employer starts jacking him around or terminates him the moment he's on company property to let us know and we will move his hire date up as soon as possible,

This is sound advice. Park the truck for home time, clean it out that night except for what minimal items you would need for a week and pack those in a separate bag that is in your car. Inform them that you're giving notice and see how they respond. Some will try and find out why you are leaving to correct the issue and retain you, others will demand the keys on the spot, and the rest are a little bit of everything in-between.