Stacker´s chock This wheel chock is designed to work with Valterra´s Stackers RV leveling block system. Place in position, drive onto the Stackers and the chock stops the RV wheel at the top of the stack. It´s that simple and makes leveling a one person job! The Stacker´s Chock also includes a built-in handle for secure nesting onto the STackers leveling blocks as well as easy carrying.