Here goes, this is for my 2011 FLHR. Made from a piece of 2'' by 3/16'' steel, heated and bent to fit into the slot in the factory seat..
This piece is for height adjustment..
Pretty basic really. Just remember that most of the touring backrests that I've seen have a 3 bolt pattern and I didn't want a big piece of metal showing so I found a backrest off a Deuce(supposedly) at a swap met for $30. A few coats of primer and paint and 3k miles later all's good..
The steel thickness also has just the right balance of flex/firmness