Dumbbell pullovers

Hold the dumbbell evenly in both hands, lay crossways or lengthwise on the bench (if your lower back is an issue) and stretch back behind the head and pull forward using the latissimus dorsi.  Pivot at the shoulder joint to work the lats, not at the elbow, which would work your triceps.  Keep your shoulders pulled down and tight.

People with poor shoulder mobility should avoid this exercise, and use straight arm pulldowns instead, and add scapulae adduction to their routines to increase shoulder and scapular mobility.