Hi Ed,
I friend who used to fly the big 747 called them leading edge flaps.
He also told me the plane even when no passengers were on can't roll back to lift off.
I remember sitting right next to the wing on a 737 and when we took off the leading edge was hanging down, the mid section was separated and the trailing edge flaps were down.
I was able to see all the hydraulic cylinders and lines and trying to figure out how the wings were generating lift.
Then at around 5,000 feet you can gear the motors or pumps going on and off and in another minute the wing looks like a one piece unit.
Very complex and amazing they fly for years and suffer little structure failure
Thanks for the post
Vegas/