supported in a suitable frame not shown of a papermaking machine wherever dewatering a fabric belt or web is desired the rolls 12 and 14 extend in a cross machine direction transverse to the direction of travel of the continuous fabric 16 and are the same length or longer than the transverse width of the fabric the top roll 13 is a rotatable cylindrical roll and has a covering 18 of rubber or other deformable material on its outside surface unlike the leading and trailing guide rolls 12 and 14 the top roll 13 has an adjustable center axis 19 adjustments in the position of the center axis 19 can be either manual or by way of an automatic control in response to an electrical or mechanical signal preferably a non contact sensor 30 detects the position of the trough portion 17 and sends a signal to a controller 31 which is connected to an actuator not shown operable to move the roll 13 toward and away from the guide rolls 12 and 14 adjusting the position of top roll 13 in relation to the guide rolls 12 and 14 varies the amount of indentation of the deformable cover 18 at the leading and trailing nips 11 and 15 which regulates the length of loop 20 and hence the radius of the trough portion 17 preferably the minimum indentation required to grip the fabric 16 is used at the lead nip 11 while a greater.