Creasing and slotting apparatus for use in producing carton blanks from a moving sheet of material, the apparatus comprising a pair of driven shafts one of which carries rotary creasing heads each having a formation adapted to engage the moving sheet to crease same, and the other carries rotary slotting heads aligned respectively with said creasing heads in the direction of travel of the sheet and each having a pair of spaced arcuate slotting blades one of which is movable with respect to the other around the axis of the associated shaft such that the distance between the blades and thus the slots cut thereby is adjustable, there being a first compensator means for selectively rotating the slotting heads while the associated shaft is stationary or in motion, to enable the heads to be positioned in register relative to the moving sheet, and second compensator means for selectively rotating the shaft carrying the creasing heads in a likewise manner, there being a driving connection between said creasing head shaft and each movable slotting blade on the other shaft, whereby the relative positions of the fixed and movable blades can be adjusted during drive.