After it is splinted and put in a sling, there is not much else you can do to immobilize it. You could have the victim move as little as possible.
A splint and sling are what immobilize the extremity.
Swathe
Swathe
Swathe
Swathe
It is called a swath or binder.
Cloth or improvised swathes of fabric. SABC-Swathe
Cloth or improvised swathes of fabric. SABC-Swathe
Cloth or improvised swathes of fabric. SABC-Swathe
Cloth or improvised swathes of fabric. SABC-Swathe
Cloth or improvised swathes of fabric. SABC-Swathe
A splint and sling are what immobilize the extremity.