A common use of the shop floor system is to allow for the re-assembly of finished goods. For example; a customer may want a configuration of a computer or another item that you don't have in stock. However, you do have a computer that is similar and some parts in inventory (or another computer you can disassemble) that will allow you to produce the desired part.
In this case, you can create a BOM that describes the transaction required to re-assemble the part you have into the part you need. The following example illustrates how this type of BOM could be set up.
Top Level Item
Computer with 80GB Drive
1 Computer with 40 GB Drive
-1 40 GB drive
1 80 GB Drive
In the above example, the Computer with 40GB drive, and the 80GB drive are the components that are pulled from stock. The 40GB drive is a by-product that will be added to inventory once the shop order is completed.
The system is intelligent enough to properly update the consumption accumulators in the inventory master with the correct information based on parts being produced and consumed by the Shop Floor system. This is important as this usage and production information is used by the purchasing system.