Bee
                
              
              
                  
                  
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              There is a version here:
To put it lightly the frame is a fulcrum for the router.  It is thought the best angle is somewhere from 10 - 17 degrees.
You might want to look here first:
More information is here:
from here: ( warning 800+ post )
Let me know if you have a specific question, I’ll do my best to help.
Thank you