Rubrics allow you to create assessment criteria for scoring assignments. To add a rubric to an assignment, first navigate to Assignments in the course menu. Click on the name of the assignment, then select +Rubric. This link provides more information adding a rubric to an assignment: https://community.canvaslms.com/docs/DOC-2870. You can also visit this link for details on how to use a rubric to grade in SpeedGrader: https://community.canvaslms.com/docs/DOC-1928.
