Method of positioning thin flat objects within a processing machine comprising an inserter for positioning these objects in a plurality of gripper members belonging to a conveyor drawing them discontinuously through successive stations. This method consists in calculating, for each of the gripper members, variations in the positioning distance of these members relative to a reference position, assigning these variations to the respective gripper members, and incorporating them into a primary procedure of the controller to improve the positioning of the thin flat objects in the gripper members.