On occasions when I leave my bike locked up at a train station or bus station, I use 3 u-locks to secure my bike.
Abus Granit-X Plus 54 Mini for the Rear Wheel to the frame
Abus Granit-X Plus 54 for the Front Wheel to the frame
Abus GRANIT Extreme 59 for Frame to secure object at train station or bus station(with my helmet also secured by this U-lock).