^ we do this as well sometimes.
an incident I was involved in was not the kingpin but the edge of the trailer near the kingpin. I was doing whatever and turn toward the trailer and all I saw was a flash of light and pain. Hit the right side of my forehead on the edge of the trailer when I was going under to get something from the front compartment. Nice bruise on my noggin. I still don't know what I was thinking, I knew it was there, had been under that thing 20 times right before it. Just did not duck enough that one time. It hurt.