3. Stone steps
My favourite of them all—at least to look at. Typically, these project from the flanks of a dry-stone wall and are simply undressed treads without risers. They are not only part of the fabric of the wall, but also have that cantilever quality, which requires a certain faith in the mind of anyone using them. All is typically well until you reach the top, when realisation dawns that you will have to pirouette to face the other way before descending the other side, as the stones are the same on both sides. These are, reasonably enough, called through stones (pronounced thruff in northern parts).