Page "Millstone" Paragraph 16

The furrows and lands are arranged in repeating patterns called harps.

A typical millstone will have six, eight or ten harps.

The pattern of harps is repeated on the face of each stone, when they are laid face to face the patterns mesh in a kind of " scissoring " motion creating the cutting or grinding function of the stones.

When in regular use stones need to be dressed periodically, that is, re-cut to keep the cutting surfaces sharp.