The document provides two feedback keys that you can choose to your preference. I use both in my classroom. The first page is used as informal grading to provide quick feedback on things like exit tickets. The second is posted on the front whiteboard and used as I circulate my classroom and aggressively monitor. This can be used for any subject, in any class, for any activity. It increases immediate feedback to more students for them to adjust their mistakes as well as decreases the time it takes to check on every student.