It was just a door ... connecting the inside to the outside. On this day, when the handle was pushed downward, the door swung open,  to be caught by the wind and pulled wide. People would pass though, on about their business. A moment later, it would swing back, closing with a loud crash ... a boom, shaking the area and causing those sitting nearby to unconsciously jump in their seats.  

In and out people would go, touching the door only to open it, paying no attention as to what would happen when it was let go. They were busy, they didn't have time to notice, and they didn't care. So on it banged.  

One woman noticed. As she passed through, she kept hold of the handle, allowing the door to open only enough so that she could pass through. She then eased it closed behind her. No crash, no boom, no jumping. Only a careful open and close ... conscious and deliberate.

She stood out. It was a simple detail, but it made all the difference.