The broad purpose of the occupation is to produce complex high value, low volume components or assemblies in full or part, using machines, equipment or systems, to the required specification. For example, turbines, cranes, gearboxes, production lines, rigs and platforms.

Fitters may typically have a mechanical, electrical, electronic, control systems, pipe fitting or instrumentation bias. To produce or re-furbish the components fitters will interpret drawings or specifications and plan their work, for example ensuring they have the right tools, equipment and resources to complete the task to the required specification. Fitters are required to check their work against quality standards.