Masks
Used to create a Scrolling Marquee

Open Flash

Go To Modify>Page Properties
Set the Stage size to 50 pixels high
300 pixels wide.

Set stage color to black.

In the First Layer Insert>Motion Tween

Paste the text into the first layer

Align the top of the text with the stage


 
Go to frame 200, Insert a keyframe

Move the Text so the Bottom of the text aligns with the stage

 
Insert a New Layer

Draw a Rectangle over the stage
(shown in blue)
Select layer 2 (with Rectangle)
Right Click>Mask

The rectangle will now act as a Window

Save

Go to Control>Test movie