# Part-Procedure Relationship
Procedures may be associated with one or more parts to relate a workflow with a specific workpiece. Link a part and a procedure from the **Parts** tab on a procedure. Note that this isn't a parts list that are in an assembly - by setting this relationship you are telling ION which procedures are used to produce a certain part or assembly.
You can also set up the part-procedure relationship from the parts library sidebar.
When you link parts through this relation when you have the "Require part-procedure relationship to be approved" box checked in your organization settings, ION will not allow you to create runs unless the selected part is linked to the selected procedure.
With this box checked, when you attempt to create a run with a procedure that is not linked to the selected part, you will get an error that looks like this:
#### Required vs. Optional Part Procedure Relationships
When linking parts to an inspection procedure, the **Required** or **Optional** setting determines whether an inspection run is automatically created upon receipt.
* This toggle **ONLY** effects **INSPECTION** type procedures their parts upon receipt.
* **Required:** When a part marked as *required* is received, an inspection run is automatically generated for that part according to the associated procedure.
* **Optional:** When a part marked as *optional* is received, no inspection run is automatically created. You can still initiate an inspection manually if needed.
This setting helps control which parts must go through inspection by default and which can be inspected at your discretion. See it in action below.
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