40 locks over center line 60 carriage 14 is moved to a forwardmost position in slot 12 an end of carriage 14 may be inward of slot 12 and extend beyond the housing 3 however carriage 14 may not move more forwardly owing to step 15 see also fig2 which interacts with the end of slot 12 in the position shown in fig3 lever 36 has moved counterclockwise so that bar 32 and gripper arm 30 have rotated to grip printed product 5 fig4 shows a perspective view of the gripper unit 1 as shown in fig3 housing 3 includes first side 10 second side 110 and a top side 11 which can run on track 2 shown schematically second side 110 has a slot 112 in which a carriage can slide also near second side 110 of gripper unit 1 is a cam 146 supported on a v shaped shaped hinge 140 having a first arm 142 and a second arm 144 fig5 shows the side of gripper unit 1 opposite the side shown in fig3 second hinge 140 is locked over center by a second cam follower 150 acting on cam 146 arm 144 of hinge 140 is rotatably connected to a pin 148 and to a pin 145 arm 142 of hinge 140 is connected to pin 145 and to bar 32 a carriage 114 is slid forward in slot 112 by the action of cam 146 which is forced downwardly by cam follower 150 a latch 136 is attached rotatably by a pin 137 to carriage 114 so as to be act clockwise about pin 137 this clockwise force can be effected for example using a spring or alternately can occur.