Fly (clothing)

A fly (UK: flies) (short for flyers) is an opening on the crotch area of trousers, closed by a zipper (often), or buttons. On men's garments, the fly always opens to the right; on women's garments, it may open either to the left or to the right.^[1]

A fly can also be on other garments, like the paletot coat of the 20th century, where it is the front opening that can be secured close and is covered hidden by fabric.