Abstract: Corrugating rolls for forming corrugated paperboard medium are given a flute valley profile having a narrow channel along the valley base between arcuate segments of the valley base that parallel the channel on opposite sides of a radial plane of symmetry. This valley base channel is of such depth as to relieve the fiber compression stress between cooperatively nipping flute tip and valley surfaces along the axial plane between respective corrugating rolls. One advantage of the invention is to increase the on-line time of plated rolls by limiting accelerated wear of the plating in the valley base channels of the rolls. The invention also provides an improved corrugating medium characterized by flute tips which are relatively less compressed as compared to adjacent flanking regions.