Bolts are used to join pieces together either permanently or temporarily. Many steel structures, including buildings, are simply bolted together. For example, the Eiffel Tower in Paris was originally a temporary structure and after twenty years it was to be dismantled. For this reason most of the steel components were bolted together. However, the tower has lasted well over a hundred years. Much of the structure of the Empire State Building in the USA is also bolted together. Nuts and bolts can also be used to fix together small structures such as furniture. Nuts and bolts come in many different types and sizes and some are shown below.