Originally Posted by
AndrewP
U-lock to lock the rear wheel to the frame, so the bike cannot be ridden + a hardened steel chain (also linked to the U-lock) to go around your concrete post. Hardened steel chain is not as easy to cut as a cable.
And a chain to lock your seat and another to secure your front wheel. Because riding a bike with neither is no fun. Or pull your seat and take it with you.