2003 GMC Sonoma Owner's Manual - Page 32

When you sit in a center seating position, 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 on page 1-30. 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. 1-25