Some original builders used wedges, slides or whatever you want to call them. These wedges were sometimes headed with a small formed head and sometimes just a slightly wedge shaped piece of sheet stock. Most were made of iron, but I have seen them made from brass. They seemed to run around .040 thick and few exceeded 3/8" wide at the widest point. they were carefully fit to wedge tight and then dressed off to the surface of the stock. Many were carefully made and fitted, while others seem rather crude. Then as now you had all levels of builders and price brackets for work. Of course I assume some that you see are replacements, crudely made to replace wedges lost long ago.
