Wrap, as used in the phrase "That's a wrap", has been used by directors since the early days of the film industry to signal the end of filming. Since the 1920s, filmmakers have been using this phrase when principal photography is concluded and the film is ready to go into post-production. At that point, it is traditional to hold a wrap party for the cast and crew of the film. This marks the end of the actors' collaboration with each other, the director, producer, and crew on the film. However the leading cast members may be called in several months or years later to help promote the film when it is ready to be released.