How to map a URL to a specific template?

Please place below code in your theme’s functions.php file & let me know how it goes 🙂

add_action('wp', function(){
    list($uri, $qs) = explode('?', $_SERVER['REQUEST_URI']);
    if ( $uri == "/arbitrary/path" ) /* Change this to path that you want to match*/
    {
        locate_template( "template-full-width.php" , true, false ); /* Don't forget to replace template name with actual template which you want to load */
        die(); /* So that WordPress does not load its template as per template hierarchy. */
    }         
});