What is the vertical width of the flag when it is flying free called?

The term that defines the vertical width of a flag when it is flying free is known as the hoist. In flag terminology, the hoist refers specifically to the vertical part of the flag that is attached to the halyard or the pole. It contrasts with the fly, which is the horizontal width of the flag that extends away from the pole.

Understanding the distinction between hoist and fly is crucial for proper flag etiquette and usage, especially in naval and maritime contexts. The hoist measurement is important as it can affect how a flag is displayed, folded, and stored. For example, flags often come in specific proportional dimensions, where the hoist and fly measurements are defined to ensure the flag maintains its intended appearance and symbolism when displayed.