I just dumped my US stuff for Euros. There are three plastic knobs that hold the frame in place. Here's a link to the part: http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1M213UQ821M213UY3G&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1981&product=P8010-16255&application=000025003