The term 'SEMI FILLER' is a job description for a DIESEL mechanic. A DIESEL mechanic is responsible for maintaining and repairing DIESEL engines, which are used in many types of vehicles, such as cars, trucks, buses, and boats. They must be knowledgeable in the workings of DIESEL engines and be able to diagnose and repair any issues that arise. They also need to be able to perform routine maintenance on the engine, such as changing oil and filters, and checking for any signs of wear or damage.