Board Buddies [BBs] is a unique product and come in various configurations allowing clockwise, counter-clockwise, and free spin versions.  First, I confess I've only seen these in action as I own a now defunct version by Leichtung Workshops (sp?) that uses flat rollers that are toe'd in rather than BB's cambered rollers.  When mine become unserviceable, Board Buddies will be on my short list of things to buy.  Why?