The Lying One Arm Rear Lateral Raise is an advanced exercise that will target your rear deltoids.
Steps
Lie on a bench, facing towards the ground. Grip a dumbbell in one of your hands and let it hang off the side of the bench. Make sure the bench is high enough so that the dumbbell does not touch the ground.
Raise your arm by contracting your deltoids. Hold this top position for a second then slowly lower the dumbbell back to the starting position in a slow, controlled manner.