Level luffing crane

A level-luffing crane is a crane mechanism where the hook remains at the same level whilst luffing; moving the jib up and down, so as to move the hook inwards and outwards relative to the base. Usually the description is only applied to those with a luffing jib that have some additional mechanism applied to keep the hook level when luffing. Level-luffing is most important when careful movement of a load near ground level is required, such as in construction or shipbuilding. This partially explains the popularity of fixed horizontal jibs in these fields. [Level luffing crane. Wikipedia]