Lock a source to a specific frame. For the duration of the clip, only the source front and source matte at the selected frame is used.

To lock a source:

1. Select the source you want to lock.
2. Using the playback controls, choose the frame at which you want to lock the clip.
3. In the Source Front option box, select Front Lock.

   
   

   A check mark appears in the L column of each selected source.

4. In the Source Front option box, select Front On to unlock the source.