Sinew
Cordage 
Sinew
is made from the ligaments and tendons of an animal's body.
Tendons
and ligaments are made of thick, closely packed bundles of collagen
fibers.
Tendons form flexible cables that connect a muscle to a bone. Ligaments
are similar to a tendon, but connect one bone to another bone.
The tendons
of large animals such as big horn sheep, deer, elk, moose, and bison
were used for sinew.
The
tendons would come from the animal's hind legs or from along both sides
of the spine beginning at the neck and running just past the ribs.
In
the illustration at right, the tendons from an animal's hind leg are
colored red, blue and yellow. These are the tendons from which sinew
would have been produced.

Sinew
is very strong and is an excellent material for thread, bindings, and
bowstrings.
The
sinew was prepared soon after the animal was slaughtered. It was scraped
clean with an obsidian tool to remove all the natural glue. Then the
sinew was soaked in water, and rubbed between the hands to soften it.
After
the sinew was rubbed, the fibers could be stripped off with an awl or
a sharp obsidian tool.
To
process the tendon into cordage it could also be pounded with rocks
or chewed in the mouth to soften and loosen the fibers.
Sinew
cordage was applied moist so that it became stiff as it dried. Sinew
thread was used for sewing clothing.