Adding comments about your rules files is a way to record how you intend your rules to work.
For instance, you might want to record what a particular rule permits or denies. This type of information will save you hours of time in the future. If you ever need to fix a security leak quickly, you will need these comments to jog your memory. You might not have the time to figure out what your rules meant, so use comments generously.
Each of the dialogs associated with creating and activating packet rules has a Description field. This is the field that is reserved for your comments. The system ignores anything you put in this field. You might want to use the comment field at each step of the rule creation process. This can reduce your chance of forgetting to make a significant comment. It is best to make your comments while the process on which you are commenting is still fresh in your mind. However, you can wait until you finish creating all your rules.
For instructions on how to make comments in a rules file, use the Packet Rules Editor online help.