The picture is the jig built for making the ribs, the blocks of wood help hold the tubes in place while Drilling and riveting the gussets. The circle at the top of the picture is for marking and cutting the main spar rib flange.
Here is a rib in progress and the last photo shows several completed ribs. Note the air drill and rivet puller. I don’t think I could have done the job without them. While reading an article in “Kit Planes” I saw a repair in progress. After pulling a few rivets by hand, it did not take long to convince myself it was a necessary.