I assume when you say "cut the ends" you mean miter. If so, don't. When installing crown molding you should cope rather than miter. The concept of coping is rather difficult to explain in words - try going to a library to research the subject or find a friend to show you. Basically, what you do is create a profile of the moldingby cutting a miter; the profile is then cut away with a coping saw (coping) and fitted to the adjacent piece. Outside corners are mitered.