Abstract: Adhesive coated front edge faces of successive stacks of paper sheets are bonded to downwardly folded marginal portions of flap-over covers at an aligning station which receives stacks from a first source along a first path wherein the stacks are caused to advance at right angles to their adhesive-coated edge faces and which receives covers with adhesive-coated marginal portions from a second source. The covers move along a second path lengthwise of their marginal portions and in parallelism with the front edge faces of the stacks in the first path. Each stack which arrives at the aligning station is disposed behind the downwardly bent marginal portion of the corresponding cover and is thereupon moved with the cover through the nip of two rollers which apply external pressure to bond the marginal portion to the edge face of the corresponding stack.