This is . I added this code to the spot where I want the anchor link to appear:

<?php if($this->item->params->get('itemAttachments') && !empty($this->item->attachments)): ?>
<!-- Anchor link to item attachments below - if it exists -->
<li>
<a class="itemAttachments" href="<?php echo $this->item->link; ?>#itemAttachmentsAnchor"><?php echo JText::_('Attachments'); ?></a>
</li>
<?php endif; ?>

And this code where I want the anchor itself to be positioned: 

<a name="itemAttachmentsAnchor" id="itemAttachmentsAnchor"></a>

i.e. just above the class itemAttachmentsBlock.