On the chain there is a device called the trolley.
How to attach a garage door arm to the chain.
Using pliers remove the cotter pin from the cotter bolt that attaches the upper end of the door arm to the carriage.
Swivel the arm down and allow it to.
Press down on the chain with your finger.
Pull the chain toward the garage door and hold it in position.
The exact location varies depending on the door.
You should have 1 2 inch of play in the chain.
Thread the nut s facing the door clockwise until it meets the bracket then release the chain.
There is a threaded eye bolt that can be adjusted to get enough slack to attach the chain.
Attach the bracket that connects the arm the door is opened by one arm that raises it as the carriage travels along the tube.
Pull out the cotter bolt with the pliers.