A system is provided for sorting solid materials, that system comprising: a plurality of shafts disposed upon bearings, the bearings being fixed on an inclined slope; each shaft of the plurality of shafts being configured with a plurality of sorting discs, the sorting discs being configured with a receiving cavity and material contact fingers; spacers configured to be received by the receiving cavity of the discs and to maintain a desired space between the discs; and the spacers being configured with a hexagonal or pentagonal cross section.