Sit next to elevated surface, approximately arm pit height. With hand of arm next to elevated surface, grasp unilaterally loaded dumbbell; thumb next to side with weight. Bend elbow approximately 90-degrees and place upperarm on elevated surface. Position thumb downward (pronated).
Rotate dumbbell so thumb turns upward (supination). Return and repeat.
If unilaterally loaded dumbbell, or "half dumbbell" is not available, grasp conventional dumbbell to one side of handle with pinkie against inside surface.