PART NO.  SPL.PAGE  DESCRIPTION                                                            
AFH1899   15.R.2    Stiffener -door casing (2) -(body shell, Tourer, 1500)
AFH1899   16.R.2    Stiffener -door casing (2) -(body shell, 1600 and 1600-MK-II Tourer)
AFH1899   TC.O.2    Stiffener -door casing (2) -(body shell, Tourer, Twin Cam)

Part number AFH1899 is a formed steel bar with a top curl, to be attached to the inboard side of the door shell with pan head tapping screws. The top curl is to nest over (on top of), the lower edge of the opening in the door casing card, which is for access into the door pocket, thereby stiffening the door casing.

Click on image below to get a full scale drawing of this part in PDF format. This drawing can be printed full scale on ANSI D-size paper, 22x34-inches, centered, with 1/2-inch margins all around, to be showing the 21x33-inch border line.

The space inside the top curl is shown as 0.156-inch. This is as measured on a commercial part procured in 1986, which has served the purpose well for decades. The door liner panel (casing) is expected to be made with nominal 1/8-inch thick plywood, covered with thin vinyl in the specified interior color. In recent times, plywood manufacturers may be expected to skimp on the designated thickness by about 10%, making nominal 1/8-inch plywood more like 0.112" thick. My recently measured vinyl covering material is 0.022" thick, making the wrapped edge of the panel 0.112+0.022+0.022 = 0.156" thick. As drawn, this stiffener would be a snug fit on the edge of the vinyl covered panel. It is also common for a replacement stiffener bar to be formed with slightly less than 180-degree bend, leaving a little more space inside the curl, enough to allow for paint thickness. If you were to make your own stiffener bar, you might measure your fabricated vinyl covered panel first, and finish forming the stiffener curl accordingly.