Subaru 2005 Impreza Owner's Manual page 407

Maintenance and service
5. To install the air cleaner case cover, insert the
three projections on the air cleaner case into the slits
on the air cleaner case cover and then snap the two
clamps on the air cleaner case cover.
11-26
Turbo models
UGB094BA
1. Unsnap the two clamps holding the air cleaner
case cover.
USB521BA