Open Flash and click on the size button on the Properties panel to open the Document Properties dialog box. Give the document a title and set the width to 300 px and height to 100 px. Set the frame rate set to 30fps ( frames per second) and press ok:
Double click on the text Layer 1 and name it text.
Click on the text tool on the Tools panel and set the font size and type on the Properties Panel then click on the stage and type some text:
Select your text with the selection tool and at the Align & Info & Transform dialog box click the align horizontal and align vertical buttons. Make sure the To stage is selected.
Add a new layer by clicking the add layer icon on the Timeline:
Name this layer effect.
Lock the text layer by clicking on the dot under the lock:
Select the effect layer. Make sure you are in the 1st frame.
Click on the Rectangle Tool (R). Turn off the stroke color and select black as your fill color (click on the arrow by the paint bucket below select black instead of yellow).
Draw out a rectangle in the 1st frame of the effects layer:
With the Selection Tool select a little piece of rectangle and then press delete on the keyboard.
Make small rectangles by selecting and deleting all the way across the rectangle:
Select all the triangle by dragging an imaginary box around it with the selection tool. Click F8 to convert it to a symbol. Give it a name at the Convert to Symbol dialog box and select graphic as the type.
You should still be in the 1st frame of the effects layer. Drag the rectangle symbol to the left of the stage:
Click in Frame 30 in the effects layer and click F6 to insert a keyframe. Notice that your text has disappeared. Click in the 30th frame of the text layer and click F6 to insert a keyframe there.
Click back on the 30th frame in the effects layer and align the rectangle to the center of the stage:
Click in frame 60 of the effects layer and insert a keyframe by clicking F6. Click in frame 60 of the text layer and insert a keyframe there.
Click back on frame 60 of the effects layer and move the triangle to the far right of the stage:
Click in frame 90 and insert a keyframe on both the text and effect layers. On the effects layer center the triangle on the stage.
Click in frame 120 and insert a keyframe on both the text and effect layers. On the effects layer place the triangle on the far right side of the stage where we had it positioned in the first frame.
Now we need to create a motion tween on the effects layer between frames 1 and 30, 30 and 60, 60 and 90, and 90 and 120. You can add all the motion tweens at once by clicking anywhere between 1 and 30 and then holding down your left mouse while dragging down the frames and stopping somewhere between 90 and 120:
Select motion from the Tween options on the Properties panel.
The last thing is to make a mask. Right click on the effects layer and choose mask from the drop down list:
on the Properties panel to open the Document Properties dialog box. Give the document a title and set the width to 300 px and height to 100 px. Set the frame rate set to 30fps ( frames per second) and press ok:
on the Tools panel and set the font size and type on the Properties Panel then click on the stage and type some text:
and at the Align & Info & Transform dialog box click the align horizontal and align vertical buttons. Make sure the To stage is selected. 
![Flash 8 Masking Layer]](rightclickmask.gif)
