The special design of the split device allows the columns of tree trunks , regardless of length and diameter . The riving knife is here driven by the oil piston of the lateral surface in the trunk , while the reaction force is absorbed by the invading into the end face of the stem cross- cutting . In fibrous wood and long trunks , the device can be fitted transversely ( see picture left ) . This can be expanded to 220 mm width of the gap as often . Through the use of the portable device , the columns of pulpwood can significantly simplify and speed . be more severe split crowns or root portions , the more economical is the use of the device . The scissile pieces are lying once in their respective positions on the ground as needed , or cut several times .