Subaru 2004 Impreza Owner's Manual page 49

Seat, seatbelt and SRS airbags
Be sure to fasten both tongue plates to the re-
spective buckles. If the seatbelt is used only as
a shoulder belt (with the connector's tongue
plate not fastened to the connector's buckle on
the right-hand side), it cannot properly restrain
the wearer in position in an accident, possibly
resulting in serious injury or death.
1-22
1. Remove the tongue plate from the belt holder locat-
ed under the right rear quarter glass and pull out the
seatbelt slowly.