Creating Ext. Ops. With Service Specification Ref. 
Use
When you create externally processed operations based on service specifications (see
Service Specifications), you can use the general task description as stored in the service specifications. You must describe how to perform the task in the operation of your maintenance task list - not in the service specifications - as only there can you enter materials, production resources/tools, personnel and so on.As a maintenance task list is exploded in a maintenance order, the system creates a purchase requisition that also refers to the service specifications used in the operation.
For a detailed description of service specifications and external services management, see the documentation MM - External Service Management. The following topic merely describes how to include service specifications in maintenance task lists.
Procedure
You are now on the screen for external processing.
A pop-up window will appear and the system will ask you if you want to create a hierarchy.
If you answer
YES , perform steps 5 and onwards.If you answer
NO , perform step 6.To call up the individual service lines for a grouping level, double click on the level.
You are now on the screen for maintaining service specifications in externally processed operations.
You can also select the service using the menu bar sequence Service specs.
® Service selectionIn the pop-up window that appears, select the purchase requisition or purchasing object you want to use as a reference. The system copies the specifications to the service lines in the externally processed operation.
The system copies the purchase quantity and the corresponding quantity unit from the service lines and shows the net price summed up for this operation. You can no longer change the data in the screen for external processing.

On the screen for external processing data, you may also refer to an outline agreement or outline agreement item. The system automatically transfers this reference to the purchase order requisition when an order pointing to this task list is released (see documentation MM - Purchasing).