If an item or part type is no longer going to be used, it can be deprecated. This is sometimes a good alternative to deletion and could serve as a temporary solution while waiting for an opportunity to delete, etc. 

When the Is Deprecated option is selected, users can no longer create items of that the item type or any of its sub-types. The option does not affect any existing items in the database of the type. Although the Is Deprecated setting is inherited by sub-types, It is recommended that you still check the Is Deprecated box for each sub-type as well. 

In the above example, users will no longer be able to create items of the types "Package" or "Product". However, they will still be able to view these types of items and search for them if they chose to.

The Is Deprecated option can easily be revoked at any moment by de-selecting the option.

Description References

The Description References feature of the platform is unique and the creation of references differs from the creation of items/parts. Description Reference cannot be deprecated in the same way as items and parts. If you select Is Deprecated and there are no Description references in the structure, users will not be able to turn them "on" in the structure using the View menu. However, just as with items and parts, if it is set to deprecated and instances of Description References already exist in the structure, users can still turn them "on or "off" in the tree using the View menu. So for Description References, the Is Deprecated selection only affects the viewing of them. Users can still create them in Descriptions.