Rules hold a special fascination for collectors -- their aren't many users of these old folding rules left. Rules are made of exotic materials such as Turkish boxwood, African ivory, and German Silver, much of which just isn't available any more today. Rules, with their highly precise graduations, are a miracle of production -- the earliest ones were hand marked by someone with the patience of Job. Rules were used to measure distance, of course, but some also had additional scales marked on them to measure the volume of casks, the amount of timber in a log, logorithms, or other engineering data. Rules can be very small or very large in size.