You are right that we cut down an old header for these shelves. We found the headers at an architectural salvage shop in our local area. The headers were lightly sanded with 100 grit sandpaper to remove any rough wood or areas that would give splinters or catch on fabric.
To attached the shelves to the wall we used: ½” diameter galvanized piping, floor flange, 3” screws and a spade bit. We started with locating the studs in the wall to set the spacing for the anchors. With the studs located we could then set the location of the floor flanges. These were installed on the wall directly over the stud. (Make sure you get good secure purchase here because this will be holding up the shelf and everything on it.) Use the threaded hole in the floor flange to located where a 5/8” hole will be drilled. This 5/8” hole for is to receive the ½” galvanized piping. A hole was drilled (very carefully) straight into the center of the header on the side of the board at the floor flange location. This hole will need to be around ½ the depth of the shelf so it will be easy to get off course and drill through the flat portion of the shelf so be careful, go slow and try a test on a scrap piece of board first.
With that you will need to screw the ½” piping in the floor flange and slide the shelf on the, now installed, piping. (When picking up the piping from the store you can have them cut it there. You will need to plan to have one threaded end on each of the pipes you plan to use as a support.)
Using this method of installation these shelves should not be loaded with much stuff. My guess is that you shouldn’t put any more than about 10 lbs. on the shelf. This will be best used as a decorative shelf and not a storage shelf.
Hope this helps!

I forgot to mention that the finish on the shelves is a lightly tinted beeswax.