Boston Celtics Zipper Thumb Sideline Out of Bounds August 21, 2013September 17, 2014 Kyle Gilreath This sideline out of bounds play from Doc Rivers and the Boston Celtics is one of my favorite plays. Zippering a guard into a middle pick & roll is extremely effective and opens multiple scoring options. Share this:TwitterFacebookEmailLinkedInPrintLike this:Like Loading...