Thanks to Guy Pursey of CCC
Position vehicle on a level surface facing perpendicular to flat wall at a distance of 10 metres (about 33 feet). Mark on wall width of vehicle (W) and height to centre of headlamps (H). Mark centre of headlamps (C). Suspension in 'normal', ENGINE RUNNING (on cars with automatic adjusting or hydropneumatic suspension).
Adjust headlamps using dipped beam only. Adjust screws to position the deflection in beam pattern at (C). Ensure horizontal width portion of beam is parallel to (H) and approximately 15 - 20cm.(6-8") below line.