Abstract: This invention relates to improved apparatus for forming paper board structures in which two corrugated mediums are bonded together at their flute tips. The apparatus comprises: two register rolls for ensuring that the mediums are brought into precise flute tip to flute tip alignment for bonding; dependent electric motors to drive the register rolls in which one roll is driven by a reference motor and the second register roll is driven by a follower motor; location sensing devices associated with each register roll to measure a value related to the location of a position on the periphery of each register roll; control means which compares the measured values for each register roll and if necessary adjusts the voltage or current of the follower motor to maintain alignment of the flute tips of the two mediums.