docs

README.rdoc

@@ -7,6 +7,17 @@ maintenance.html page and display that instead of incoming requests.
 
  sudo gem install rack-maintenance
 
+== Usage
+
+ # config/environment.rb
+ config.middleware.use 'Rack::Maintenance',
+   :file => Rails.root.join('public', 'maintenance.html'),
+   :env  => 'MAINTENANCE'
+
+The `:env` is optional. If specified, all requests will be shown the
+maintenance page if the environment variable is set. If `:env` is not
+specified, the maintenance page will be shown if it exists.
+
 == Note on Patches/Pull Requests
 
 * Fork the project.