If you’re ever going to leave your bike on a car’s roof, it’s important to know how to lock it. There are a few different ways to do this, but the most common is to use a bike lock. To use a bike lock, first remove the key from the bike. Then fit the key into one of the holes on the rack and insert the other end of the key into one of the holes on the bike. Push both ends of the key into each hole until they’re fully inserted. Now put your hand over one of the bars on top of your bike and push down so that both ends of your key are now touching your hand. Now twist both keys so that they turn around each other - this will create a loop. Now put your other hand over top of your first hand and twist both keys together again so that they form a second loop - this will create a third loop. Now put all three loops around either side of your bike and hold onto them with one hand while you pull up on one end with the other hand to tighten everything up. You should now have an effective lock!