ну вот схематически примерно так http://www.google.com.au/imgres?imgurl=http://thecarseatlady.files.wordpress.com/2010/06/tether2.jpg&imgrefurl=http://thecarseatlady.wordpress.com/latch/latch-101-the-basics/&h=339&w=350&sz=19&tbnid=hBkT7bueCgMnaM:&tbnh=129&tbnw=133&zoom=1&usg=__LPsZBmbKSA2tTs1MlFWe8kkca7A=&docid=Ucd690CrfV8XxM&sa=X&ei=GlduUriiN8nOkgWHpoCwCg&ved=0CC0Q9QEwAA