apparently the pics I attached do not work. Here once more, the black wheel under the seat is the one which makes it all

here seat fully back, see the red arrow
http://tinypic.com/usermedia.php?uo=...sKG4h4l5k2TGxc
here the seat fully forward, see the red arrow
http://tinypic.com/usermedia.php?uo=...Bmc4h4l5k2TGxc