Affectionately known as "scripty," this position calls for noticing and managing the minute and seemingly inconsequential set details that are actually a really big deal. For example, a glass of water that goes from half empty to totally full in the middle of a scene by way of multiple takes is considered a major gaffe, sure to be torn apart in film blogs.
Famous examples of continuity calamities are easily found in pics like "The Shawshank Redemption," where bullets go from strewn about on a table to neatly placed to scattered again, and "The Godfather," where a car windshield is scattered one moment and miraculously undamaged the next [source: Movie Mistakes].
The script supervisor must take copious notes on the scenes, record the numbers and duration of the takes, as well as whether the actor had his jacket buttoned or not in the shot. Most will supplement their notes with some digital photos.
"No one thanks them for all their work, but they do hear about every single mistake they make, whether it's a mislabeled take or a B camera that is on roll B134 and not B135," explains Mike.