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Engaging manual mode on your garage door while it's open may cause it to come crashing closed if the door spring is damaged. Avoid this by setting it to manual mode while the door is closed. If this is impossible because the door is stuck open, move on to the next step. Use 2x4s that are as high as the garage door opening. If you don't have 2x4s that will fit the opening, you can improvise by placing a sturdy item like a shelf in its place. Use a hammer to tap the planks in between the door and the floor on each side of the garage door opening. Using something sturdy to prop up the door will prevent it from slamming shut, even if the garage door spring is damaged. The manual release cord is usually red and located next to the garage door motor. Pull down on this cord to disconnect the trolley from the automatic opening system. Pulling the cord will allow you to manually open and close your garage door. Have someone help you as you manually close the door. Remove the 2x4s by tapping them out with a hammer as someone holds the handle on the door. Once the 2x4s are removed, slowly and carefully lower the garage door to the closed position. Prevent the manual release cord from getting caught on the garage door tracks by pulling it down and towards the motor when you're opening the door. If you have trouble doing this yourself, ask someone for help. If you want to set the garage door back to automatic mode, you'll need to pull the manual release cord towards the door opening while simultaneously opening the door. Doing this should reconnect the trolley to the automatic opening system and allow you to automatically open and close the door with the button again.
Ensure that the door is closed, if possible. Prop the door up with 2x4s if it's stuck open. Pull down on the door's manual release cord. Remove the 2x4s and manually close the door if it was stuck open. Pull the cord towards the garage door motor to open the door. Pull the cord towards the door opening when engaging automatic mode.