Abstract: Apparatus for changing the orientation of stacks of paper sheets has two parallel transporting units each having at least one belt conveyor with outwardly extending bristles which engage the stacks and reduce the likelihood of unpredictable slippage of the lowermost sheets of the stacks relative to the adjacent reaches of the belt conveyors while the stacks are advanced from a stack supplying conveyor to a stack receiving conveyor. At the same time, the stacks are caused to change their orientation by turning about axes extending at right angles to the adjacent reaches of the belt conveyors as a result of travel of the conveyor or conveyors forming part of one of the transporting units at a speed which is greater than the speed of the conveyor or conveyors of the other transporting unit. Each belt conveyor can have an outer layer of velour with a pile of outwardly extending bristles, an inner layer of textile fabric, and a synthetic plastic intermediate layer which is bonded to the inner and outer layers.