2. Self-service bookcases are generally composed of main cabinets and auxiliary cabinets. The use of auxiliary cabinets is mainly to increase the number of books stored. It is managed by the main cabinet, and the user operates on the main cabinet, so the general price is determined by the number of main and auxiliary cabinets. You can ask the relevant manufacturers about this. For example, the following is the combination of the main cabinet and the auxiliary cabinet.