Wrought iron
As a consequence of the way in which they were manufactured, wrought iron components could not be made to fit together by interlocking (as could those of cast iron) and thus had to be connected by bolts or rivets.
As far as jointing is concerned, the major difference between cast and wrought iron lay in the method of production. Whereas each sand mould for cast iron made a piece that was tailor made for its purpose, wrought iron sections were mass produced by rolling. The rollers squeezed out elements of constant cross section from semi-molten billets. These were then cut to lengths as required. Due to this method of production the rolled elements were of small cross-section and relatively short length. The industry produced a large range of different sizes and shapes of cross-section - angles, bars and plates - and the larger and more complex cross-sections required for beams, girders and columns had to be built up from these mass-produced items. The rolled elements did not fit together, however, as cast iron elements had done; they required some extra connecting piece, such as a bolt or rivet, before a joint could be made.
