Yea, I remember when i did my first smoke system... I needed to figure out how to get that regulation. My first thought was to get an air-regulator for an aquarium. I remember having a nice brass one as a kid, and I though it would be perfect.

So I went to the local Pet Store and nowadays all they had were plastic ones that were much larger than the old brass jobs - They had a few brass type, but they were multi-valve (Like 3 or 4) and pretty pricey.

So I had a delema. I thought, "There's gotta be a simple way to pinch a line". I was thinking all I needed was a "U" shaped piece of metal that I could drill and tap a hole in, but where could I find one?

Then I hit upon the idea of the dowel, and Voila!

BTW, another neat trick is if you have an old carb lying around, you can swipe the needle valve out of it and use that.