Non-prismatic shank fasteners, such as nails, for wood and similar soft materials have a plurality of longitudinal extending non-congruent sections having different geometries, different configurations, and varying diameters such that the shank has the widest nominal diameter arranged to span a joint between wood members being fastened. The shank has four circumferentially symmetrically disposed grooves and ridges having dimensions within pre-determined ranges such that the ridges have sufficient strength to withstand the forces imposed on the shank being driven into the parent material and to resist loads imposed upon them by the loads to the parent material. The grooves have a sufficiently wide jaw opening to allow elastically compressed parent material to enter the groove and provide support to the shank. The non-prismatic grooved shanks demonstrate significantly greater load handling capability than that possessed by other known types of fasteners.