I had a great job in high school. I was a movie projectionist in our small town theatre. I got to watch a lot of movies while working and even got free popcorn! I am not sure if things are done differently now but back in those days (early 80s), we had to mount about 6-8 film reels per movie and time the switch between projectors just right. Have you even noticed while watching a movie little circles showing up in the top right corner every 20 minutes or so? Those "queue dots" are the warning to be ready to switch projectors. Such a fun job!