Wooden handled contraption found in Victorian attic...what is it?

My curiosity is getting the best of me. This contraption is made of wood (not sure what type) and has a handle that pulls down over the wooden block that could possibly create a tight fit if something were inserted between the two pieces. It was found attached to the wall in the attic of an old Victorian house. I'm thinking it was used for holding a clothesline. Does anyone know what this is and what it was made for? It is marked Cavendish (Vermont) on the top of the large block so it appears to have been manufactured and not a home-made widget. The gnaw marks on it are from mice.