My Grand Mother once had my Uncle Billy install some windows. He installed them all backwards. When I told her the windows have a problem. She said, "no there is not". She was sitting at the Kitchen Table. So, I went outside and opened the window. My Mom was sitting there too. She aske, how did you do that?" So, I closed and locked the window from the outside. At that point, My Mom told Grand Mother, all the windows were installed backwards.