HTML

<tr>
 <td class="outerleft">bla</td>
 <td>bla</td>
 <td>bla</td>
 <td>bla</td>
 <td class="outerright">bla</td>
</tr>

CSS

td {
 border-top: 2px solid #000;
 border-bottom: 2px solid #000;
}
td.outerleft {
 border-left: 2px solid #000;
}
td.outerright {
 border-right: 2px solid #000;
}