and true to her word , the girl led them along its trails , shelves , handholds and footholds with the assuredness of a nimble , hooved creature ; she knew by sight which parts of the vertical rock were treacherous and shouldnt be held on to , what wide and sturdy-looking ledges were in fact ready to crumble at the slightest pressure , and where the granite was coarse enough to sit and rest without fear of slipping off .