According to the lean philosophy there is always room for improvement in all processes, a process can always become better. Lean is about looking at a process from a holistic point of view, identifying areas where there is waste and find small improvements every day.This master thesis aims to answer the question how lean can contribute to process knowledge and sustainable improvement work. In order to receive a deeper understanding of how lean can be applied in real life the authors chose to do a case study at a production site. AGA Knivsta is a newly rebuilt maintenance site for gas cylinders, which has great room for improvement concerning productivity as well as employee satisfaction.According to the large amount of literature studied, l...