What is the origin of the idiom "hair's breadth" and when to use it?

The idiom "hair's breadth" originates from the idea of using the width of a single strand of hair as an extremely narrow and precise unit of measurement. It has been in use for centuries to describe a very small or minimal distance, gap, or difference. This expression is used to describe an extremely narrow or minimal measurement, gap, or difference. It emphasizes the idea that something is very close or nearly identical, with only a tiny margin of difference.