Historically, during the Renaissance era, most books were not shelved but stored in wooden benches, which had tables attached to them.
Each bench was dedicated to a specific topic.
The books were chained to these benches, and if a reader took out a book, the chain remained attached to it.
Until the early 17th century, academics were also allowed to borrow books.
For important books, the pope himself would issue a reminder slip.
Privileges to use the library could be withdrawn for breaking the house rules, for instance by climbing over the tables.
Most famously Pico della Mirandola lost the right to use the library when he published a book on theology that the Papal curia did not approve of.
In the 1760s, a bill issued by Clement XIII heavily restricted access to the library's holdings.

The Vatican Library can only be accessed by 200 scholars at a time, and it sees 4,000 to 5,000 scholars a year, mostly academics doing post-graduate research.
Historically, during the Renaissance era, most books were not shelved but stored in wooden benches, which had tables attached to them. Each bench was dedicated to a specific topic. The books were chained to these benches, and if a reader took out a book, the chain remained attached to it. Until the early 17th century, academics were also allowed to borrow books. For important books, the pope himself would issue a reminder slip. Privileges to use the library could be withdrawn for breaking the house rules, for instance by climbing over the tables. Most famously Pico della Mirandola lost the right to use the library when he published a book on theology that the Papal curia did not approve of. In the 1760s, a bill issued by Clement XIII heavily restricted access to the library's holdings.
The Vatican Library can only be accessed by 200 scholars at a time, and it sees 4,000 to 5,000 scholars a year, mostly academics doing post-graduate research.
Vatican Library