The chain is fastened to the bike rack with a padlock.
After you have unlocked the bike, you just leave the chain hanging from the rack.
When you return, you wrap it around the bike, insert the pin, and then re-lock it with the app.
If you need to lock the bike temporarily during your rental session, we provide a cable lock with each bike. The code to the cable lock is located above the name of the bike in the app.