Keeping your bike locked up is unfortunately a necessary precaution in most urban areas. Since you don’t need a key to operate it, or a title to prove ownership, anyone can simply walk up to it and ride off. There are many types of locks on the market, which, for the most part are going to do the same job. After all, if a thief wants your bike bad enough, they’re going to bring the tools to bypass the lock. But for the most part, just having a lock will deter most would-be bike snatchers.
So if most bike locks are going to do the job, why not just make one from items around the house? All you really need is some chain, a padlock and some fabric. The hardest part is sewing the fabric around the chain, which will not only make it look better, but help protect your bike frame a bit from the harsh metal. Once you’ve sewn it up, just wrap it around your bike and something anchored to the ground.