Sometimes a video can be the best explanation

Explaining how to use Scapular Adduction at the bottom of a pull-up, then swiching to Scapular Abduction at the top of the movement can sometimes be better explained by showing what's going on. Why would you do this? Because it works your lats much harder, and it hits all those nice muscles throughout the middle of your back. Makes Pull-ups that much better of an exercise.