Careers in this occupation field are practical by nature and involve the use of tools, machinery and equipment. People in these careers are more interested in getting on with the job, not spending time with the theoretical explanations behind the work. For this reason most of these careers have some aspect of manual labour and include tasks such as, building, fixing, constructing or producing. The choice of which trade will depend on one's interests, the industry, materials used or level of complexity. For example some people have a preference for one industry over another: aircraft, motor manufacturing, building or printing industries. Alternatively, a person may like the materials used in that trade: wood (carpenter), metal (boilermaker), brick or stone (stonemason). Some people choose a trade because of the level of complexity (skill) required in doing that task. For instance one's interests may differ according to the complexity of the devices used, i.e. electronic vs. electrical device, diesel vehicle vs. petrol driven vehicle.