Many holdings of the Main Library are kept in closed stacks. This means that, with the exception of frequently used reference works, the majority of the holdings are are not on the open shelves in the reading rooms. Therefore, you have to request books to be able to use them.
Oversize books (shelf marks III, IV, V) as well as books that are older than 100 years can be used in the reading room for old books (Lesesaal Altes Buch).permission to enter the closed stacks by arrangement. This is currently not possible due to the Covid-19 lockdown.-->