The Plains Indians were migratory people, following the buffalo. They necessarily had to carry their clothing, tools, dried food and special personal items as they traveled. They developed  parfleche cases, which filled this need.

One of the main forms of parfleches were folded envelopes of cured rawhide, decorated with painted geometric designs on the outside. The hide was stretched, scraped to a uniform thickness with animal hair/fur removed, and then dried over a smoky fire. Tribal customs of paint design evolved over time, although the individual had latitude in the painting of his parfleche. http://www.marcyburns.com/beadwork-and-wood-collection/plains-parfleche-case-probably-nez-perces