The joining of metal components by a localized fusion is a technique used with a number of arc welding processes; it can be accomplished with both manual and mechanical procedures.Early applications used the older, established processes of bare metal arc welding (with light flux-coated metal electrodes) and submerged arc welding. With these processes, welding was predominantly limited to the heavier gages and thinner plate thicknesses.In some cases to insure penetration, the welding was done through a prepared hole in the upper member of the joint; this is commonly referred to as plug welding.Although arc spot welding using the above-mentioned processes was not extensively used as a prime process, it was used for repairs and for tacking components together to hold them in relation for subsequent processing.