The solar filter should be located at the front of the optics and not in between the main objective and the eyepiece. Older telescopes may come with a solar filter that attaches to an eyepiece - do not use these. If they happen to crack, they will no longer serve as an adequate solar filter and could result in eye damage if used. The following web sites are vendors of solar filters and viewers. These are not endorsements for any particular solar filter or viewer, but resources for learning more.
Viewers are cardboard glasses that allow for naked eye observation of the eclipsing sun.
The filter is typically a Mylar sheet. The image at left shows members of the Columbus Astronomical Society posing for a picture with their solar viewers on after a successful eclipse trip to Germany in 1999. Do not look through a telescope or binoculars with these filters on. They are meant solely for direct observation of the sun without any additional optics. More information about solar filters with some very interesting technical data can be found at the Sky and Telescope web site about eclipse viewing safety .