The attention which has been paid in recent years to joining processes, such as soldering, welding, has made "built up" construction both rapid and efficient, and it is often cheaper than "one-piece" manufacture. The main types of joining processes are riveting, soldering, welding by electrical, fusion welding, plasma-jet welding,etc.

A weld has been described as the whole of metallurgy in miniature, for it calls for the knowledge of the melting , casing ,and forging of metals.