Caution: You can lose control of the vehicle if you try to adjust a manual driver's seat while the vehicle is moving. The sudden movement could startle and confuse you, or make you push a pedal when you do not want to. Adjust the driver's seat only when the vehicle is not moving.
If the vehicle has a manual seat, it can be moved forward or rearward.
Try to move the seat with your body to be sure the seat is locked in place.