Stockable and Transactable

In what instance would you want an item to be Stockable but not Transactable?

When an item is already in

When an item is already in inventory but you dont want to do any transactions on them for various reason.... Suppose One of the item failed in customer site / during quality inspection /audit...then you might not want the item /or one of its component not to be transacted unitl the reason of failure is known