A hold is a service that allows you to reserve books that are currently checked out by other users. Through the Library Catalog, you can request to be notified when the book becomes available for you to pick up.
To place a hold, simply go to the Library Catalog, find the item you're interested in, and click the "Place Hold" button on the item's record. Then, enter your student number and follow the steps to confirm your request. For more details, check the guide "Make holds from the Library Catalog."