title: What does the "mount" instruction mean in Rails routing?
body: <p>I cannot find the meaning of the keyword "mount" in <a href="http://api.rubyonrails.org/classes/ActionDispatch/Routing.html" rel="noreferrer">Rails routing system</a>.</p>
  
  <hr>
  
  <p>I have set up <a href="http://jejacks0n.github.io/mercury/documentation/" rel="noreferrer">Mercury</a> to use within my Rails application. It added this line to my <code>routes.rb</code> config file:</p>
  
  <pre><code>Appname::Application.routes.draw do
    mount Mercury::Engine =&gt; '/'
  </code></pre>
  
  <p><strong>What does the <code>mount</code> keyword mean?</strong></p>