Abstract: Sizing apparatus adapted to modify particle size. First and second sizing rolls are mounted parallel to each other and define a trough therebetween which receives material to be worked. The material moves through the trough toward a gap between the rolls. An end closure is adjacent first and/or ends of the sizing rolls, and closes off an end of the trough. The end closure comprises a support structure, and an array of interface elements mounted to the support structure and spaced with respect to each other to provide, optionally in combination with the support structure, an effectively continuous interface surface to contact the material being worked. The interface elements comprise working surfaces which move in cooperation with movement of the material.