System Settings Panel
Here you set system defaults. For example if you are going to catalog a stack of paperback books you would change the default Media Type to "Softcover Book" so you wouldn't have to change each one as you are cataloging. Or if a due date falls on a holiday when the library is closed you can set the "Due Date Overriede" field to a date when the library is open and this will override the due date that would otherwise be assigned at each checkout.