Buick 1994 Century Owner's Manual page 46

Lap Belt
When you sit in a center seating position, or in a station
wagon third seat, you have a lap safety belt, which has
no retractor. To make the belt longer, tilt the latch plate
and pull it along the belt.
To make the belt shorter, pull its free end as shown
until
the belt is snug.
Buckle, position and release it the same way as the lap
part of a lap-shoulder belt. If the belt isn't long enough,
see "Safety Belt Extender" at the end of this section.
Make sure the release button on the buckle is positioned
so you would be able to unbuckle the safety belt quickly
if you ever had to.
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