Why is last-child not working?

I am trying to give my table td's a border-bottom apart from the last td. Where am I going wrong?

CSS

.rack  {
    border-left: 15px solid #959595;
}

.rack td {
    border-bottom: 15px solid #f05f28;
    width:100%;
}

.rack td:last-child {
   border-bottom: none;
}

HTML

<table class="rack" width="600" border="0" cellspacing="0" cellpadding="0">
  <tr>
    <td>&nbsp;</td>
  </tr>
  <tr>
    <td>&nbsp;</td>
  </tr>
  <tr>
    <td>&nbsp;</td>
  </tr>
</table>

FIDDLE