Do you want a near thief-proof security chain for your precious bicycle? Are you willing to pay a little extra and, perhaps more importantly, are you indifferent as to its weight?
Then proceed as follows. Buy 3 or 4 feet of Pewag 3/8" square security chain (about $12 per foot excl. tax/shipping, Westech Rigging is one supplier), one Abus 82/70 keyed padlock (about $20 excl. tax/shipping from Zoro or similar) and some heavy duty canvas. Wrap the chain with the canvas and secure at each end with vinyl electrical tape or similar.
When locking your bike, if at all possible, run the chain through the rear wheel as well as the frame. If you are using this for your auto bike rack, get enough chain to go through frame + both wheels. If you are using it for hanging out at SXSW on your mountain or city bike, you might have to take your chances with the front wheel.
BE WARNED: my 3-ft version with lock weighs about 6½ pounds !!!!