An intrinsic part of the overall process of fabrication of finished components or products inevitably involves the joining of individual parts of the whole. Metal joining processes most commonly involve fusion of a component part of the joint; for example: soldering, brazing or welding, or involve mechanical fixings. Generally, those relevant factors relevant to the joining of metals are incorporated within the chapters that deal specifically with the particular materials. Nevertheless, the editors feel it useful to include this more general article, which was included in previous editions of Shreir. Although its details are now clearly somewhat dated, its overall grasp is still valid. Note that this chapter has been edited for structure and consistency only and that no significant attempt has been made in updating it.