What does Rose used to splice together the previews mean It is in a book I am reading that takes place movie theater.?

In the context of a book set in a movie theater, the sentence "Rose used to splice together the previews" suggests that Rose had a role in creating the previews that were shown before the main movie. Splicing is the process of joining two or more pieces of film together, commonly used in film editing. By splicing together the previews, Rose would have been responsible for selecting, compiling, and arranging the short segments of upcoming movies or advertisements that were played as part of the theater's presentation before the main feature began.