Subaru 2003 Legacy - Manual (Page 422)

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4. If the new blade rubber is not provided with two metal spines, remove
the metal spines from the old blade rubber and install them in the new
blade rubber.
HS0192
Metal spines
5. Align the claws of the metal support with the grooves in the rubber
and slide the blade rubber assembly into the metal support until it locks.
Be sure to position the claws at the end of the metal support between the
stoppers on the rubber as shown. If the rubber is not retained properly,
the wiper blade may scratch the windshield.
HS0194 HS0193
Stopper
6. Install the wiper blade assembly to the wiper arm. Make sure that it
locks in place.
7. Lower the wiper arm.