Apparatus having two spaced rolls with a plurality of intermeshed disc-like teeth. The rolls form a nip into which an absorbent board is fed for partial slitting. The board is comprised of both long and short fibers. The apparatus separates the short fibers at each slit while leaving a number of long fibers intact to maintain a unitary structure. Advantageously, the teeth of one roll form gaps slightly wider than the thickness of the long fibers with the teeth of the other roll to permit passage of the long fibers.