Phantoms and ability to book inventory

Hi all,
We are at release 7.6
We have many of a certain type of phantom in our bills of material. Our
business practice is that we do not book inventory on a phantom and have
no labor under it, just materials.
If there is a need to book inventory at that level, we change it from a
phantom to a WIP part and put labor under it.
Since these parts are so similar in nature, our concern is that someone
might accidentally book to a phantom. I know that we have to hitch up
these phantoms to a warehouse for MRP to work, so not giving it a
warehouse is not a solution.

Is there a way to flag these phantoms so inventory could not be booked?
Any ideas?

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