"On reserve" means that the book is set aside for use by a particular class. You can check the book out using your NUID, but usually only for a short period of time. Items can be checked out for a few hours or several days depending on the item and the course. Course reserve materials are also limited to one checkout at a time. For example, you will only be allowed to check out one model, book, or movie at a time.
Online course materials are available through Canvas:
Login to Canvas
Select the course from the Dashboard
OR go to Courses, and then select the course you want to open.
Look for "Libraries Course Materials" link to access online course materials.
