This is a special collection apart from the main stacks. Just bring the book's call number to the Reference Librarian who'll page it for you. Some Mezzanine books may be checked out. Others are for room use only and will require leaving your ID at the Circulation Desk.
These are rare, especially valuable or historically significant items housed behind the Circulation Desk. Bring the call number to the desk and the book will be paged for you. The desk will hold your ID and you'll be able to consult the book in the library.
The Cooper Union Library
7 E 7th St.
New York, NY