Optimal shoulder immobilization is achieved when the upper arm and forearm are secured to the chest. Traditionally, this has been done with a sling that supports the elbow and forearm and counteracts the weight of the arm. The simplest sling is a triangular bandage tied behind the neck.
Additional support is provided by a swath which wraps around the humerus and the chest to restrict shoulder motion further, and keep the arm securely in the sling.
Commercially available devices provide similar immobilization, with or without the circumferential support of a swath.