It is measure of distance between the plan of the fork, with the staft fully deployed, and the ground. The effective useful height is,in reallly, less, since we have to subtract the height from the ground to the plan of the fork when it in its lowest position – depending on the model truck, of course in many trucks, the fork call be lowered to the ground. The useful lift height depends in the height of construction and also the type of staft.