I understand how easy it is to be doing something over and over again, and not see what you're doing. I had a job where I was installing 6 panel interior doors for every room of that house. I forget how many there where, but it went on for a couple of days. When I was done and cleaning up, I noticed that one of the doors where upside down. I installed it with the small panels at the bottom and didn't see it. I walked by it a dozen times, maybe two dozen times, and didn't see it. But when I saw it, I couldn't believe it. I just stood there and looked at it like it had arms and legs. It wasn't hard to flip it how it should of been, but the shock of seeing what I had done, and never saw until days later just blew my mind.