A crane is a little bit like a puzzle. It consists of many different parts. Some fit together, some do not. With all the parts, a device has to be built, which has to operate efficiently and safely. This paper will only consist about two large crane families: the mobile cranes and the tower cranes. The mobile cranes include the crawler cranes, the truck cranes and the mobile construction cranes. The tower cranes can also be divided into two large groups: the self-erecting cranes and the top-slewing cranes. The capacities of the crane system are large. Thanks to the variety of jibs, of substructures, of tower combinations, of climbing elements and operations, of moving equipments, etc. almost all technical needs can be satisfied. Depending on the selected equipment, a crane can cover a very wide range of work. The crane is a key component of the construction site. His problems can totally obstruct the good running of the work. Well designed and clever selected, the crane is a guarantee for the success of a safe and efficient building site. However, althought we can find in the literature many technical documentation and crane data from the various manufacturers (documents and informations on the dimensioning of the boom, the tower etc.), a complete document which describes and analyzes step by step the anatomy of the cranes is hard to find. The present paper deals with the different applications of a crane on a building site. With considerations about the right number, the best location, and the operating costs, an optimal use of cranes on building sites must be warranted.