How to set an UNUSED col as USED again

The ALTER TABLE tablename SET UNUSED COLUMN colname CASCADE CONSTRAINTS statement is apparently used for marking a column as UNUSED..
I tried loking up a few books including Chip Dawes ..However none of the book mention how to Unmark a UNUSED Column.(so that the column becomes visible again while viewing the table definition !!)

Would appreciate if someone could give me the syntax for setting an UNUSED column as USED again
Thanks- Sunnny

drop it and re-add it

Setting unused is a one-way trip. The purpose of the feature is to "hide" the column for now and be able to drop it later when it is more convenient (implying that dropping the column involves large amounts of data, don't want to impact the database during the business day, etc.).