Can anyone tell me if there is some type of trick to installing the lock and lock cylinder on a 66 glove box?

If I recall, the case unscrews out of the outer trim ring. I remember installing mine and holding the outer ring by hand ( fingers ) tight to thread the lock in to place.

Does the trim ring have a notch? or the lock case? one of those is held while the other is threaded.

Been a while i could be wrong.