Field help (SOQFMI) 

Use this field to choose how to cover the requirement expressed by the order line: in a normal way, using a receipt back-to-back order, a direct back-to-back order or a production back-to-back order.

Based on the product category and the setup of the product record (Sales tab), this field is initialized in the following way:

For kit components, this field always defaults to the Normal value.