E-flite P-38/F-5E Lightning 400 ARF - Manual (Page 15)

15 E-flite P-38/F-5E Lightning Assembly Manual
  5. Attach the control horn to the outside of the rudder
using the backplate and two 2mm x 12mm screws.
Note: Make sure to mount the horn on the outside of
each rudder.
  6. Position the rudder against the fin. Use a felt-tipped
pen to mark the location of the hinges onto the fin.
  7. Use a hobby knife to cut slots for the hinges in the fin.