Reading stones has taken me some time to understand. I feel the process is like learning a new language and I'm still learning. I love it!
I'm going to start with what I call gauged stone. I use this term since the stone I'm showing "Butler stone" happens to have similar sizes thickness. Such as 1", 3 inch high....ect...ect
The stone shown has a undercut. The Face ( face-the part of the stone which faces the out side of the wall -IE what you see) of the stone can be placed on the wall 2 ways (for conversation)
the correct (above)
Working with your batter creates a structurally and visually correct wall. (batter - is the angle of the wall in which it may lean. My wooden frames leaning from left to right)
The face of this stone should flow in the same direction as the batter. Not against it (above). A stone may fit great into your space -BUT-The stone above should be shaped by knocking off the undercut. Making the face a bit more flat. As time would have it - best to work with the stones as much as possible not against them.
Moral of this blog - if your stone looks like this Flip it over to work with your batter not against.
What do your stone faces look like?
Notes: How to read stone faces is a never endless topic. I will continue to talk about my journey to understand them. These views are only my opinion.