Subaru 2004 Legacy Owner's Manual page 53

Seat, seatbelt and SRS airbags
3. After confirming that the webbing is not twisted, in-
sert the connector (tongue) attached at the webbing
end into the buckle on the right-hand side until a click
is heard. If the belt stops before reaching the buckle,
return the belt slightly and pull it out more slowly. If the
belt still cannot be unlocked, let the belt retract slightly
after giving it a strong pull, then pull it out slowly again.
1-28
UB1033BA
4. Insert the center seatbelt tongue plate in the center
seatbelt buckle marked "CENTER" on the left-hand
side until it clicks.
UB1034BA