The strap is 1/4 inch wide and 35 inches long. It is meant to go
through the grommets on the hat brim (or through slits made by the owner
on earlier style campaign hats without grommets) and can be worn either
around the back of the head or under the chin. These straps are
actually a bit long for either application, but that is how originals
were made and that is how I copy them. Apparently most users cut them
to fit themselves and in most cases made a new hole. This style strap
came into use around 1912 and was used through WWII.