title: Django 1.8 - Intermediary Many-to-Many-Through Relationship - What is the consequence of where 'ManytoManyField' is used?
body: <p>An example Many-to-Many through relationship in Django:</p>
  
  <pre><code>class First(models.Model):
      seconds = models.ManyToManyField(Second, through='Middle')
  
  class Middle(models.Model):
      first = models.ForeignKey(First)
      second = models.ForeignKey(Second)
  
  class Second(models.Model):
  </code></pre>
  
  <p>Following the <a href="https://docs.djangoproject.com/en/1.8/topics/db/models/#intermediary-manytomany" rel="noreferrer">documentation on intermediary models</a>, only one model of the pair to be related contains the <code>ManytoManyField</code>, model First in the example above. Is this correct?</p>
  
  <p>If so, which model should contain the <code>ManytoManyField</code> field? Are there any differences in using the relationship from either end depending on where the <code>ManytoManyField</code> is?</p>
  
  <p>Thanks</p>
  
  <p><strong>EDIT (I should have been clearer):</strong></p>
  
  <p>I'm interested in an Intermediary table because I will have additional data to store on the relationship.</p>
  
  <p>When I say usage, I don't mean defining the models, I mean using the relationship (otherwise I'd let Django do it's thing).</p>
  
  <p>If I want all Seconds related to a First, would it be exactly the same as getting all Firsts related to a Second, or would the <code>ManytoManyField</code> make one direction easier to do than the other by introducing any extra functionality?</p>