Tower Cranes have become a fixture amongst city skylines throughout the world. Tower cranes are generally fixed to the ground on a concrete slab. Different types of tower cranes include Top-Slewing, Bottom-Slewing, Flat-Top Tower Cranes, Hammerhead Tower cranes, Self Erecting Tower cranes and Luffing Jib Tower cranes. A Tower crane rotates on its axis and the long horizontal jib is the part of the crane that carries the load. The counter-jib carries a counterweight, usually of concrete blocks, while the jib suspends the load to and from the center of the crane. Tower cranes are generally used in the construction of buildings.