An assembly for movement according to predefined rules of motion, includes a supporting frame forming a working path that accommodates a driving element with which at least one movable element is associated which is adapted to move an item to be subjected to a process. The assembly includes, interposed between the driving element and each respective movable element, at least one movement adjustment apparatus having a contoured guide, arranged substantially parallel to the driving element, at least one first lever that has a first end that can slide within the guide, and a portion that is pivoted to at least one second lever which in turn is coupled rigidly to the driving elements. The first lever has a second end, which is opposite the one that can slide in the guide, which is articulated to a linkage, which in turn is pivoted on a portion of a respective movable element.