The opener trolley will engage the carriage once it comes to the full open position.
Overhead garage door engage and disengage.
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.
It might be necessary to pull the door closed slightly to fully engage the trolley.
Some garage doors do not have a manual lock once disengaged from the garage door opener.
Push the control button either on a remote or at the wall station to operate the garage door opener.
Make sure the carriage unit is nearest to the garage door.
Re engaging the garage door to the electric garage door unit.