Chevrolet 2003 Silverado 1500 Pickup Owner's Manual page 32

Lap Belt
When you sit in a center rear seat position of an extended
cab or in the center front seat position of either a crew
cab or an extended cab, you have a lap belt.
Your lap safety belt 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 show17
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 on page 1-31.
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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