There are certain situations wherein we have to support the arm most especially if we suspect an injury on the shoulder. Dislocations are very painful, and eventually an x-ray should be conducted to insure there is no other problem. The objective of an armsling bandage is to insure that the arm and shoulders are stabilized to prevent additional injury.

Locate the apex of bandage, make an overhand knot (figure 1)

Place the apex on the affected shoulder, supporting the elbow (figure 2)

Bring one point on the unaffected side of shoulder (figure 3) 

Place the other one point on the affected shoulder (figure 4)

Ask patient's comfort to make adjustment  (figure 5)

Make a square knot on the neck side of the patient (figure 6)

Fold the sides of the triangular bandage making expose the fingers (figure 7)

Insert the overhand apex of the triangular bandage on the elbow, housekeeping purpose (figure 8)

You now have the complete set-up of armsling using triangular bandage (figure 9)