Britax Safe-nSound Instructions For Installation And Use Manual page 19

G. Engage seatbelt buckle and tongue. Push down
on the seat (with knee or hand), whilst pulling
the sash belt firmly to tighten the seatbelt. This
will make the lap belt very tight across the
restraint. Whilst holding the seatbelt tension,
ensure to remove all slack from lap part of
seatbelt by pulling sash belt. For retractor
seatbelts, allow excess belt to feed back into
retractor.
NOTE: Seatbelt buckle and tongue must not
rest between restraint cover and restraint. If
seatbelt buckle is adjustable, adjust buckle
as low as possible away from the restraint.
HOW TO INSTALL
Push down on the seat
Pass buckle tongue through slot here
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