Talking about marks on monitors......in todays motion picture film cameras there's a TV camera that "feeds" off the optics as they file a scene.....this is to allow for video playback on the spot so that the director can review what's in the can without having to wait until later to view the rushes.

On that monitor are marks showing the borders of both the typical movie theater screen and conventional aspect ratio TV screens. This is to help set up the shot for eventual viewing on both mediums as video tape/DVD sales and TV broadcast are a big chunk of money.

Anthony