2D Tracking - Nuke 101: Professional Compositing and Visual Effects - page 233

5. Select CornerPin2D1 and press the M key to insert a Merge node after it.
6. Attach Merge1's B input to Read1 ( FIGURE 5.30 ).
Figure 5.30. Merging the foreground and background branches.
7. View Merge1 in the Viewer ( FIGURE 5.31 ) .
Figure 5.31. The picture now sits in the frame, but it can use some more
work.