The rocks on the Shetland west side cleave at a very specific angle.
I picked up a pebble on the beach. Many of the pebbles show this pointed regular shape. It gave me great pleasure to find that the angle matched my drawing. It is approximately 70 degrees.
The angle is visible even in the large cliffs.
Here is this sketch in progress:
The strange object in the top right of the drawing is not a drone, a cormorant, a flying fish or a small airship. It is a mistake. When I closed the sketchbook to continue my walk, some wet paint transferred itself from the left hand page to the right.