The crane's boom is one of its most substantial components. This is easily identified by the lengthy steel arm that spans the length of the machine. This section of the crane runs from the operator's cabin to the hook. The boom distributes the weight and gives the appropriate height for each load to be lifted. When the crane reaches the end of its range, it must be brought back into position for another load. This is done by an assistant operating the controls in the cab of the truck. The word "crane" comes from the Old French word for fork or pair of forks, which indicates that these machines were originally built with two arms mounted on opposite sides of a base so they could lift heavy loads. Modern cranes usually have three sections: a head, a body, and a foot. The foot section connects to the base; the body holds the main lifting mechanism—usually including hooks and cables—and it can be raised or lowered relative to the ground; the head contains the control cabin where the operator sits. These machines are used in many different applications, such as construction sites, assembly lines, and even at airfields to move large objects around. They are extremely useful tools for heavy jobs that require a lot of strength or distance be moved quickly. Here are some examples of how cranes are used: At airports, cranes are used to lift aircraft parts onto and off of trucks.