A sheet feeding and corrugating system, especially for output of image substrate sheets of a reproduction apparatus, wherein the sheets are fed in a normal path through a sheet feeding nip comprising plural spaced sheet feeding rollers. Both feeding and variable corrugating of flimsy or stiff sheets is provided by spherical balls freely mounted in generally vertical ball retainers providing for vertical movement and dual axis rotation against the sheet feeding rollers to define the sheet feeding nip and by additional similar balls (in additional similar ball retainers) intermediately of the feed rollers, which additional balls are unsupported vertically except by bottom-of-travel retainers so that these additional intermediate balls roll gravity-loaded against a sheet being fed through the nip to provide sheet corrugation varying automatically with the stiffness of the sheet, and are freely liftable up to the level of the nip by stiff sheets resisting corrugation. These balls may be readily added to or removed to independently increase or decrease the sheet nip and/or corrugation forces at their respective locations transverse the nip. A sheet side shifting mechanism can laterally offset the sheets in the same nip to eject offset, by moving only the sheet feeding rollers, without resistance from the stationarily mounted balls, all of which roll freely laterally as well in the normal feeding direction.