Add a bar at the bottom of the page that shows the template being used. Simply add to your functions.php file and comment out when done with it.

snippet.php

/*
 * Add a bar at the bottom of the page that shows the template being used.
 */
function show_template() {
    global $template;
    $style = '
        background-color:rgba(0,0,0,1);
        position:fixed;
        bottom:0;
        right:0;
        left:0;
        color:#fff;
        opacity:.2;
        padding:.5em;
        font-size:.6em;
    ';
    echo '<div style="'.$style.'">'.$template.'</div>';
}
add_action('wp_footer', 'show_template');