Maintenance engineering has traditionally been viewed as a hands-on field with strong inclination toward mechanical engineering. With advances in information technology, operations management, and manufacturing systems, such an understanding of mechanical engineering is no longer valid. This paper sheds light on what maintenance engineering means today and what maintenance is in practice. The paper is based on firsthand experiences and insights gained by the author while working as a senior maintenance engineer. It provides a conceptual guide to the skills and expertise, such as analytical skills, coordination skills and technical know-how, required of today's maintenance engineers. It also offers design principles for enhancing these skills and summarizes the findings into a design of a suitable maintenance engineer profile. The insights shared in this paper can help both academics and practitioners advance the field of maintenance engineering and bridge the gap between science and practice.