usually assembly of components, toasters, keyboards, etc. some metal stamping or plastic molding or woodworking. As opposed to a steel mill or auto plant or oil refinery. Light infers less that the town industry. The term, I believe, comes from most zoning codes that classify the industrial/manufacturing into light or heavy industry and the need for proper zoning. In my hometown the heavy industry zoning is either along the state highway or the railroad. Employment is really not a factor, as a light manufacturing plant can have hundreds or thousands of employees. It the activity and the needed amenities that make the light versus heavy classification.