The GMB is a general trade union in the United Kingdom which has more than 560,000 members. Its members work in nearly all industrial sectors, in retail, security, schools, distribution, the utilities, social care, the National Health Service (NHS), ambulance service and local government.

A boilermaker is a tradesperson who fabricates steels, iron, or copper into boilers and other large containers intended to hold hot gas or liquid, as well as maintains and repairs boilers and boiler systems.