Background masters allow objects from one screen to be visible and functional in the background on multiple other screens. Background screens save programming time and project memory. They can also help give a project a familiar look and feel across some or all of your screens. Any screen in your project can be a background screen, just select it below the screen thumbnails in the Navigation Window.

Now this menu is viewable and fully functional on both of these screens, but instead of having it copied onto both screens, it's maintained and edited in one place and it uses half the project memory.