A creasing device is provided that includes a counter-rotating male drum and female drum. The male drum carries a conventional creasing ring with a central rib flanked by shoulders. The female drum comprises a central channel aligned with the creasing rib on the male drum; and a pair of projecting lateral ribs on each side of the central channel that are aligned with the shoulders on the male drum. The lateral ribs press a sheet of the card or paper stock against the shoulders of the creasing ring to better define the edges of the crease and to reduce the tendency of a printed coating on the stock to crack during subsequent folding. The pair of lateral ribs may be provided by a pair of inserts. Alternatively, both ribs and the central channel may be provided by a single insert.

Provided herein is a device for folding a stack of sheets. The device includes a frame, means for pre-folding a stack of sheets along a crease line into a main plane such that a booklet with a straight back is obtained, means for keeping the pre-folded booklet relative to the frame, a carriage movably arranged to the frame and moveable parallel to the back of the booklet, and a nip arranged to the carriage for receiving the back of the pre-folded booklet. The nip direction forms an angle greater than zero with respect to a direction of movement of the carriage.