Whiteboard Session: Middle Back Defense for Rotational and Perimeter Defense. Whiteboard sessions is a category of videos available to members of the Volleyball University App. The whiteboard sessions use a whiteboard and marker to break down different concepts, skills, and strategies to make you a more effective volleyball player. If you want to learn more about how to become a member of Volleyball University so that you can improve as a player, comment or message me the word "Volleyball" and I