With Assemble to Order (ATO) production approach, the product is built to customer specifications from a stock of existing components. This assumes a modular product architecture that allows for the final product to be configured in this way; a typical example for this approach is Dell's approach to customizing its computers.
In the research literature, a hybrid model is often referred to as an assemble to order (ATO) system. In an ATO system, usually there is a pre-fixed set of end-product types from which customers must choose. In contrast, a Configure to Order (CTO) system takes the ATO concept one step further, in allowing each customer to configure his/her own product in terms of selecting a personalized set of components that go into the product. Aside from checking that the product so configured must “make sense”, there is no “menu” of product types that limits the customer's choice. See description to learn more about Configure to Order (CTO).