On some of the Drupal administrative pages, you will encounter a great many checkboxes. This is especially true of the permissions page (User management > Permissions), which starts off with more than six dozen checkboxes for a vanilla Drupal 6 installation. Add a typical suite of contrib modules, and the number of checkboxes increases substantially. As a consequence, you may be forced to manually check or uncheck long sequences of checkboxes, which quickly becomes tedious and time-consuming.
But there is a solution to this problem, available to anyone using the Mozilla Firefox browser: Check All is an extension that allows you to check or uncheck many checkboxes at a time. Simply add that extension to your Firefox installation, and restart the browser. If you are using one of the latest versions of Firefox, it may complain that the extension is incompatible with that version of Firefox, but you can disable that by setting extensions.checkCompatibility = "false" in about:config.
With the extension installed, on any Drupal admin page seemingly filled with checkboxes, you can highlight your chosen checkboxes using click-and-drag with your computer's pointing device (or highlight all of them using Edit > Select All), right-click on the page, and from the resultant context menu choose "Uncheck all selected checkboxes" or "Check all selected checkboxes".
Once again, Firefox extensions can save the day and, in this case, your sanity!