Abstract: A calendar stack is provided with pneumatic actuators of the expansible bag or bellows type wherein a selected roll has the end bearings thereof carried by a pair of pivoted control arms, the position of a respective control arm being selectively controlled, for upward loading or for downward loading of the stack by a single primary actuator. The selected direction of force application by the primary actuator is determined by a force transmission linkage shiftable by a secondary actuator between a first and a second position, for roll upward loading or roll downward loading.