Subaru Impreza 2.2L MT Owner's Manual page 292

Metal spines
HS0192
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.
Stopper
HS0193 HS0194
6. Install the wiper blade assembly to the wiper arm. Make sure that it
locks in place.
7. Lower the wiper arm.
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