Ask most people, and the answers you may receive are a shot and a beer or a college football team from Indiana.
The answer you will read here is quite different.

Boilermakers are defined by the work they do.

Work performed by boilermakers requires a high degree of technical skill and knowledge attained from years of experience and training.

Field construction boilermakers work on construction sites, sometimes at great heights or where working conditions may be hot or extremely cold. Boilermakers often operate potentially dangerous equipment, such as acetylene torches and power grinders. They also handle heavy parts and work from ladders and scaffolds or on top of large vessels. Boilermakers receive extensive safety training and wear personal protective equipment, including hardhats, harnesses, protective clothing, safety glasses and shoes, and respirators to reduce the chance of injuries. Boilermaker work is physically demanding and maybe in cramped quarters inside boilers, vats, or tanks. The size of materials, tools, and equipment handled by boilermakers require excellent physical strength and stamina.

Boilermakers are highly skilled workers and receive excellent wages and benefits for their hard work.