It is often useful to go back to a revision. For example you might checkout a file, make some changes, create a local revision and make some more changes. You might then decide that you want to disregard your latest changes and go back to you local revision (checkpoint).
To do this, right-click a revision and select 'Revert Back to Revision'. If the file is not already checked out, this will checkout the file and copy the selected revision data to the local file. If the file is already checked out and changed then a local revision will be created first (so you can always go back to this version if necessary).
You can then make further edits to the file and submit it as described in Chapter 5, Submitting Changes