A stacking apparatus (10) for stacking flat articles (12) on edge is provided, including a belt turn-up apparatus (20) for receiving the articles at an entry nip (26a) in a flat position and providing them to a discharge magazine (40) in an on-edge position, the belt turn-up apparatus (20) including a housing (20b) contained within an exterior frame (20a) and rotatable about a shaft (20c) near the entry nip (26a) via a screw adjustment (20d) at the egress end of the housing (20b), i.e. adjacent the discharge magazine (40), and so allowing an adjustment of the stacking apparatus (10) to compensate for different sizes of envelopes (12).