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 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.
Personal checks or money orders are fine. Your satisfaction is guaranteed with all tools. Click on the small image to see a larger version. I have the following rules for sale. Hard to find.