It's a sewing machine left to me by my mother-in-law & has no instruction manual. The only number I see is 6217C. The spool holder is vertical, but how does the tread stay on without slipping off. I have a round part than seems to fit, but it does little to keep the spool of thread from sliding off. Plus there are a lot of levers to do different things that I am not familiar with. That is why I am looking to find the instructions guide. Hope you can help.