Push in the control knob on the burner appliance to unlock the valve.
Dial the knob clockwise to the "Start" or "Light" position. Ignite the grill normally. For example, on an outdoor gas grill you press the red igniter button to light the burner.
Turn the burner control knob clockwise to increase flame height and heat from the burner. Turn the knob counter-clockwise to reduce propane flow to the burner, causing the flames to decrease in size. Use the markings on the control knob to guide your adjustments.
Return the knob the the upright "Off' position to extinguish the burner. The knob pops out to the locked position, reducing the risk of a gas leak.