If your garage door opener is malfunctioning, or if there is a power outage, you may need to know how to lock your garage door manually. It is a relatively simple process, but it is important to follow the instructions carefully in order to avoid damaging the door. First, locate the red cord that hangs down from the motor unit. This cord is usually attached to a emergency release handle. Pull the cord down until it is fully extended, then push the release handle away from the motor unit. This will disengage the trolley, allowing you to operate the door manually. Next, lift the door up until it is fully open, then pull the emergency release handle towards you to lock the door in place. Finally, close the garage door by hand until it latchis securely in place. Keep in mind that a manual garage door can be heavy and difficult to operate, so it is important to exercise caution when using this method.