Detaching a garage door from a screw drive opener system for screw drive models the shuttle release lever will be engaged and in the up position see image 1 below.
Overhead garage door engage and disengage.
It might be necessary to pull the door closed slightly to fully engage the trolley.
To disengage you ll pull the emergency release cord down which will release your garage door from the opener system.
Some garage doors do not have a manual lock once disengaged from the garage door opener.
The opener trolley will engage the carriage once it comes to the full open position.
Make sure the carriage unit is nearest to the garage door.
Pull the release rope and push the door all the way up until you hear a click.