Baffle bafflement

I'm looking at a small refractor and I'd like to know -

- where baffles should be placed in the telescope tube?
- how can you tell if a baffle is placed so that it takes away aperture?

I've got a small refractor that I'd like to review and I've got a few extra objective lenses that I'd like to assemble into small refractors.

The site Dave has referred to shows how to layout the baffles. I have found this is a practical way to install them and position them.

I string a fishing line from the objective cell to the eyepiece opening and pull it good and tight so that it defines the outer limits of the light cone as in the first drawing in the article. The baffles can then be placed so that they just come up to the line. If any of the baffles are too far forward the line clearly shows where. Once all baffles are in place, remove the line.

have fun,
dan