Locate the two slots and use a single control horn to make sure each of the two slots are cleaned out.
Doing so will make installing the fully assembled horn much easier.
Assemble the control horn as shown. Temporarily install in the control horn and cut out around the
base of it as shown. Next, glue in the control horn using either 30min epoxy, or Gorilla Glue. This
same process is used for the elevators and ailerons.