Known Error Database
A database containing the recorded solutions of all internal and possibly some external Known Errors.
ITIL defines a Known Error as a faulty CI. (Could be faulty due to mis-configuration, or 'cause there's smoke coming out of the back!).
So there it is - gloriously simple. Known Errors get found and then you put a record in the Known Errors Database. If an RFC needs to be raised to fix the CI, you do so, and if you have a workaround you attach the details to the Know Error's record.