Creating a "Film Framing" Effect in Flash

You can use that centered rectangle as a base to define your working area inside the main stage, as you build your Flash scene. This works well with still images—but for animation, you can also take this a step further, and create a frame to layer over your animation so that you don’t have to try to stay inside a certain defined area. The overlap of the frame will cover anything that doesn’t belong. Just use the Paint Bucket tool to fill the areas above and below the rectangle you’ve just sized and positioned, before selecting the black fill areas and copying them to a new layer atop everything else in your scene.