An example function for how to add a custom wrapper to a WordPress `more` tag.

more-tag-wrapper.php

<?php

/**
 * Creates a custom 'Read More' link by prepending and appending columns on either
 * side of the anchor to create a divider between the next post.
 *
 * @param    string    $link    The anchor for rendering the more tag
 * @return   string    $link    The text for the more tag
 * @package  mayer
 * @since    1.0.0
 */
function example_add_more_link_class( $link, $text ) {

	$html = '<div class="more-link-wrapper">';
		$html .= '<div class="divide col-md-5"></div>';
		$html .= '<div class="col-md-2">' . $link . '</div>';
		$html .= '<div class="divide col-md-5"></div>';
	$html .= '</div>';

	return $html;

} // end example_add_more_link_class
add_action( 'the_content_more_link', 'example_add_more_link_class', 10, 2 );