Unplug the vacuum from the power outlet. Press the handle release with your foot and tilt the handle as far back as possible.
Lay the vacuum on its side. Place your hand on the adjuster plate on the bottom of the vacuum.
Apply pressure to the adjuster plate while turning the adjustment dial. Turn the dial until the plate starts moving in accordance with the position of the knob.
Set the vacuum upright and plug the vacuum into the power outlet. Set the carpet height adjuster to the desired height and start vacuuming.