A millwright is a craftsman or tradesman who installs, dismantles, repairs, reassembles, and moves machinery in factories, power plants, and construction sites.
A fabricator is a person versed in may trades who is able to construct a complex finished product from a simple idea.
A rigger is a person who specializes in the lifting and moving of extremely large or heavy objects, often with the assistance of a crane or derrick or chain hoists.
A welder is a tradesperson who specializes in fusing materials together. The materials to be joined can be metals (such as steel, aluminum, brass, stainless steel etc.) or varieties of plastic or polymer.