Google failed me this time. Lot's of pictures but no how to do. Actually
the 4th picture down on this page illustrates the style but not the width.
It also appears to be on block and not stone:
I have to try to duplicate some of the 1920's raised mortar joints on a rock
foundation. The ones that if viewed from the left end view of a cross
section would look like
I actually failed at this once before. I tried making a "rake' in that
shape and it just did not do the job because of the unevenness of the stone.
If you have done it or know how they did it, I would love to hear from you.