These guys are more commonly known as " stand ins." There are several reasons that a studio would use a stand in back then. The most common reason would be for a situation like this one; The scene at Woltz's place may have already been shot and now Duvall is over shooting another scene at a totally different location. The scene that has already been shot could not be reviewed until the "can" got back to the studio. Meanwhile back at the studio the producers/editors may not like the way the lighting of a scene came out, the sound, or the angle of the scene. So they may have to go back and re-shoot that specific scene over again. It is too costly and eats up too much time to have a star like Duvall leave the set that he may currently be on, to re-shoot a scene that he already played in. So the studio minimizes the expense and will use a stand in or stand ins and re-shoot the scene from a far distance or a different angle so that the viewer will not be able to see that it is really not the actual star in that scene. This was common practice back then as technology was not advanced enough as it is today to allow the director to immedeatly review a scene, that has just been shot, right on location. Today with DVD technology and VHS technology a director can review the scene immedeatly, on site and just shoot it over again right there and then. So therefore in this day and age stand ins are very rarely used and if they are used then they are basically used before a real shoot takes place to check the lighting or the sound.

Don Cardi