These are Oak and I did some re-engineering of the origional design I saw years ago. I call it a "hinie-pincher" stool. If the seat isn't fully closed and the 2 top board tight together when you sit down it will really pincher your "hinney" bad. I assembled them with 3/4" dowels in blind holes. Tricky to assemble as it has to work smoothly to be open and closed and function smoothly.