Chevrolet 2000 Lumina Owner's Manual page 15

Driver's 4-Way Manual Seat (Option)
Lift the handle to tilt the seat up or down.
The driver's seat may have a bar and a handle under the
front edge of the seat. Lift the bar to unlock the seat and
to slide it forward and backward. Try to move the seat
with your body to be sure the seat is locked into place.
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