First time I got loaded at Domino Sugar in Baltimore, they locked me in to the dock, put an airline lock on, put a giant stop sign (windshield height) in a hole directly in front of the tractor, made me wait inside, and took "my keys". I asked, isn't this a bit of overkill?
They told me about drivers getting P.O.'d and leaving, running over the stop sign and dragging the tires...
