What does the plus sign (+) in a call number mean?

Plus signs (+) in call numbers mean that a book is categorized as oversized, and is shelved at the end of each call letter section. 

For example, if you see the following call number: 

F1410 +R395 2000

you will want to look for this book at the end of the F section, before the books with G call numbers. 

The Science Library does not have an oversize section.