A separator for separating stacked sheets of lumber or other building materials. The separator comprises a substantially planar top and bottom surface; the top and bottom surfaces extending substantially parallel to one another. The separator further comprises two side surfaces, each with outwardly protruding side edges for preventing the separator from resting on either side surface; and a front side and a back side substantially parallel to the front surface. A plurality of channels extend into the top and bottom surfaces with the channels defining a plateau, coexistent with the top and bottom surfaces, between adjacent channels. Each channel has one or more apertures for creating a substantially vertical airflow passage between top and bottom surfaces of the separator.