Embodiments provide systems, methods and apparatuses for positioning boards and other wood pieces in preparation for sawing/trimming. In embodiments, a continuous track loop conveys board stops slideably mounted to board stop guides positioned perpendicular to the direction of flow. A horizontal frame member provides a series of positioning guides through which a cam follower coupled to a board stop is diverted, thus adjusting the position of board stops in a direction perpendicular to the direction of flow without the use of braking devices or other added sources of mass, friction or vibration.