Use as catagory only?

I just stumbled accross a field called Use as Catagory only on inventory items.  I found it by trying to enter an inventory item using a role which has no permission to view accounts.  It is a check box. 

I don't find any documentation on this field in help. 

The odd thing is that I cannot see it in my admin role and I don't see it in the form set-up.

But I like it!  Using it we can set up catagory names for inventory items and they are not available for purchase or sale or transfer and so on.