Assemble-to-order with Variant Configuration 
You can also use assemble-to-order for configurable products. Here, the availability check can be carried out at component level only.
Configuration is carried out as usual. Depending on the selection of the strategy group in the material master record of the configurable material, a planned order, production order, or network can be created parallel to the sales order. The characteristic values assigned to the configurable material are passed on to the planned order, production order, or network. The BOM components and operations or activities you require are selected on the basis of these characteristic values.
The components selected as a result of the characteristic values are included in the availability check for assembly order processing. Any of these components that are in stock are reserved immediately.
However, only the components on the top level of the BOM are included in the availability check.
Problems occur if the BOM contains other configurable materials. Configurable materials are not kept in stock, so they are not included in the availability check. The components of these subordinate configurable materials are not checked for availability either because the availability check is restricted to the top level of the BOM.
You have the following options for checking the availability of components of subordinate configurable materials:
- You can define the configurable assembly as a phantom assembly. Phantom assemblies are not manufactured - the components are used directly in the finished product.
To define a configurable assembly as a phantom assembly, enter the special procurement key 50 on the MRP 1 screen of the material master record. However, this means that you cannot create a production order for this specific assembly.
- You can use the collective order functionality in shop floor control. Collective orders allow you to link planned orders or production orders across several manufacturing levels. For more information on collective orders, see the SAP documentation PP Production Orders Guide.
If you select assembly order processing with a network, the procedure for configuring the material depends on whether the material and the standard network are allocated to the same class or to different classes.
- Usually, the material and the standard network are allocated to the same class. Characteristic values assigned in the sales order are directly passed on to the Project System, and a network is created.
- If the material and the standard network are allocated to different classes, you assign characteristic values separately for the material and the standard network.
When a network is created, you must configure the standard network separately if the system recognizes that the material and the standard network are allocated to different classes.
If you are using assembly order processing with a network and you make subsequent changes to the configuration of the material in the sales order, the existing network is deleted and a new network is created. This is only possible if the activities in the network have not yet been processed. You cannot change the configuration of the material in the sales order once processing of the activities in the network has started.

Any manual changes to a network are overwritten when a new network is created.