Hi,
The ball was to protect the butt end during loading. Often, those ends were highly decorated with bone and engraving and the rifle had to rest against the ground to load a tight ball or patch and ball. So the ball was the stop protecting the butt end. It did not routinely house any vent pick. Generally they were fairly short and no forked rest was used. I have shot several made by Brian Anderson and they do not need any forked rest.
dave