What is this thing, dad?

My father passed away a few years ago. He had a lot of neat old tools. A master craftsman, he was also a problem solver. My question is, what problem is this widget solving? It’s a little wedge shaped thing with an attached short dowel that can easily be rotated, but will stay in position when it’s not being manipulated. If anyone has a clue, I am all ears. Nobody in the family had even a wild guess.