Coach Mike Divilbiss uses the shell drill to teach various fundamentals for man-to-man defense. The shell drill can be used to teach close outs, help side defense, defending screens and cuts and much more. This video from Coach Divilbiss demonstrates defensive principles with a pack style defense or an up-the-line style of defense. He emphasizes the mental transitions within each defensive possessions that often get overlooked. Running Time: 50 Minutes. 2005.