Abstract: A machine and process is described for squaring sheets stacked in a bundle supported along a plane. The bundle includes a leading bundle end, a trailing bundle end and opposed bundle sides. The machine includes a frame with a leading end stop mounted by a stop actuator mounting to position the leading end stop across the plane to engage the leading end of the bundle. A trailing end tamper is mounted to a trailing end actuator on the frame for movement to engage and urge the bundle against the leading end stop and align the sheets along the leading and trailing ends of the bundle. A pair of side plates are mounted by a side plate actuator assembly for movement to (a) engage and align sheets along the bundle sides and (b) position the bundle at a prescribed position on the plane.