The HT knob puts the header into auto-height control. It will go down until it feels the ground. The knobs to the right of it can be used to adjust sensitivity and ground pressure. There is also a rocker switch for the left-right "field tracker" adjustment. One of the dials on that row will allow you to adjust the balance of the sensors on the ends of the header to keep it level. Adjust that with the header on the ground and running. Don't worry about if the head is level when it is up.