title: Ruby on Rails -- multiple selection in f.select
body: <p>I have the following select box in my form:</p>
  
  <pre><code>Related Type: &amp;nbsp; &lt;%= f.select(:TYPE, [['Type A', 'Type A'],
                                    ['Type B', 'Type B'],
                                    ['Type C', 'Type C'],
                                    ['Type D', 'Type D'],
                                    ['Type E', 'Type E']
                                   ],{ :prompt =&gt; "Please select"}
                                   ) %&gt;
  </code></pre>
  
  <p>I want to allow the user to make multiple selections and also make the size of the select box 5.</p>
  
  <p>How to do that for the code above?</p>