All category of products, services or labor hours should be created as a product with differentiation based on the type of product.
Inventory movement is tracked on Finish Goods and raw materials.
Inventory movement is not tracked on service charge, dummy items and overhead.
Manufactured items are products converted from raw materials into a finish good which is physically added back to inventory till sold. eg a car or pc.
Assembled items are products converted from raw materials into a finish good at the point of sale eg burger.