What is a garage door trolley?
https://www.youtube.com/watch?v=eIbwaFxxGRE How do you reset a garage door after pulling the cord?How to Release and Reset the Emergency Cord on a Garage Door Door Must...
How does a trolley move?
https://www.youtube.com/watch?v=MKeBhAUPzgA What is a trolley and how does it work?A trolley (or trolley bus, trolley coach, or trackless trolley) is a bus powered by connection...