Abstract: A delivery for a machine processing flat printing materials includes a suction belt conveyer having conveying runs forming a support surface. To remove rejects or proof sheets as required, the delivery transports the materials along a transport path over a stack that is otherwise built up and transfers the sheets to the support surface. The physical position of the support surface can be varied while maintaining its generatrix. Therefore, the support surface can be adjusted in each print job to a working position in which secured transfer of removed printing materials to the suction belt conveyer is ensured. In a particular configuration, a latching device is provided that permits the conveying runs to escape from their working position in the event of a jam. Preferably, the latching device has a latching pin and a latching recess.