I sometimes find that my subconscious is following a tool I once used in selecting marks to make an image. I am feeling a machine and interpretting it. In this case it seemed to be a cylinder hone maybe for engine blocks, maybe for brake cylinders, maybe for a pilot bushing with only one stone. I compared this to worn out generator brushes in a 1964 Austin-Healey "Sprite" and to the riders of Husqvarna dirt bikes and a chain saw. Friction materials like carborundum, carbon, copper, asbestos, rubber, steel driven by motors or an engine under throttle control.