What is the band of material on the left side of the flag used for?

The band of material on the left side of the flag serves the primary function of hoisting the flag. This portion, often referred to as the "header" or "sleeve," is designed to make it easier to raise and lower the flag, ensuring that it can be securely attached to a flagpole or another support mechanism. By having a dedicated area for hoisting, the flag can be displayed properly without risking damage or wear to the actual fabric of the flag itself.

In addition to this primary function, the design of the band also helps to enhance the flag’s durability by reinforcing the edge where it experiences the most tension. This added support is crucial for flags that are displayed outdoors, as they are subjected to wind and other environmental conditions.