Mast Critical Dimensions And Clearances
There exists an internationally recognized standard for describing the main dimensions of forklift masts and these are shown on this drawing.
H1 is the dimension from the floor to the top of the mast with the forks lowered. (Note: the truck itself may be higher than this)
H2 is the free lift measurement. Free lift is defined as the amount by which the forks can be raised before the overall height of the mast increases. Free lift can range from almost zero to almost the same as H1. Free lift becomes important when forklifts are operating in low headroom such as under mezzanine floors etc.
H3 is measured from the floor to the top of the forks when fully raised. Maximum lift height
H4 is the highest point of the mast measured from the floor.