A Pre-cat item are created when a patron wants to check out an item that is not currently in the system. This can happen because the item was never input or because it was deleted at some point. Circulation staff create the pre-cat by entering brief information into a form and check the item out. When the item is returned, they get a message to send it to cataloging to be processed.
There are two ways that you can deal with pre-cat items at that point. The first option is to just delete the item and add it as if it were new. The second option is to transfer the pre-cat item to the correct record, adding the bib and volume as needed. Both options result in the pre-cat being in the database properly attached to a record. The first method is simpler, but doesn’t retain the information about the previous circulation. The second method is more complicated, but does retain that information.