Using matte keys

matte : a motion-picture effect in which part of a scene is blocked out and later replaced by footage containing other material (as a background painting)
1. Load 16-4.prproj.
2. Drag the theater.psd clip to Video 2 and stretch it to be the same length as the video clip.
3. Drag the Four-Point Garbage Matte Key effect from the Keying folder to the theater.psd clip.
4. Use your mouse to drag the 4 control points in the Program Monitor to the 4 corners of the sign. Changing View Zoom Level to 25% would make it easy to locate the 4 control points..
5. Set the zoom of the Program Monitor back to Fit.
6. Expand the Motion field, and adjust the Position and Rotation fields so that the sign appears in the lower-right corner. (figure)