Cable pullovers allow for a great stretch and full contraction of the lats. The added benefit of having your entire back supported by lying on the ground lets you focus on volume without the fatigue accrued by supporting yourself.
Remember, big lifts first, then do this low-stress finisher for added volume.
Gary Homann isn't your garden variety weightlifter. Sure, he's 180 pounds at 6% body fat. Sure, he had the best 500 meter indoor rowing time in the world last year in his class and he's been an ACSM certified health and fitness instructor for the past nine years. But Gary's also got a Master's degree in applied health psychology and is currently working on finishing his Ph.D. in psychology.