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Looking at the rust, I assume the door didn't latch and this needed to be transported, and once on the trailer, a larger fellow needed a hand getting "up" on the trailer so the handle was installed....
Looks like a perfectly fine latch. Slide the 2x4 forward and it clears the rear bracket allowing the door to open. Slide it back and latched again.
Just don’t hit the brakes too hard, you might unlatch your door lock.
I’m assuming the first location of the front bracket did not allow enough throw of the 2x4 and it was relocated further forward. I also assume the downward slant towards the rear is to help keep it latched while braking.