A few days ago a fellow blogger, Master Woodsman, posted a very interesting link to a document written by Walter Hough and published in 1890, cataloging and explaining in good detail different friction fire methods that were documented by the museum at that time.
This document is one of the best sources of information I have ever seen on historical use of friction fire making techniques and equipment. Not only does it provide illustrations of the tools used, it offers accounts of exactly how these tools were used and stored.
If you have any interest in friction fire making, this documents is a must read. It offers many nuances and details that have been largely forgotten over the years. You can read and download the document in different forms for free, here, or just view the PDF here (takes time to open).