Crst is horrible

Picture this.

1) Take an empty 53' dry van with swinging doors (that's your most common dry van trailer).
2) Turn it on it's nose, with those swinging doors open and pinned against the sides.
3) Now put that trailer under a conveyor belt and put 3000-5000 randomly selected items from the warehouse onto that conveyor belt and start the belt.
4) In about 30 minutes, your trailer will finally be full. While the rear is still up in the air, close those rear doors (you have to do that at that time because it's the only way to get those doors closed.).
5) Once the swinging rear doors are latched and locked, shake the trailer one time, just for good measure, then gently set it down on it's tires.

Once this is finished, tell the driver to be very careful opening the doors at the first stop.

They may be using roller carts now, but many, many years ago when I did a DG account as a fill-in, I got the distinct impression this is how the trailers were loaded.

Most (if not all) stores did not have a dock, so you had to position your trailer as close to what you think is the receiving door as possible. Just getting positioned to unload will test your driving ability.