Some garage doors do not have a manual lock once disengaged from the garage door opener.
Overhead garage door engage and disengage.
Re engaging the garage door to the electric garage door unit.
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.
Push the control button either on a remote or at the wall station to operate the garage door opener.
All you have to do to disengage it is just pull down on it and pull it toward the house and that will keep it keep the spring on the on the trolley up there extended so that it does not hang up on the trolley and then you ll be able to lift your door from the handle that should be located on one of the lower sections and you can pick your door up.
Make sure the carriage unit is nearest to the garage door.
It might be necessary to pull the door closed slightly to fully engage the trolley.