Markings

This magnificent gatepost I estimate as being over 300 years old. It stand about 6 feet tall and is very roughly cut, with signs of having been more recently damaged, possibly for being re-sited. I am fascinated by the arrow markings that have been carved into it. What do they signify and why cut them into a post that is otherwise so rough and uneven?  
It has been sunny for most of the day, which was not forecast, but there has been a cold wind to keep temperatures down.
PMQs was enjoyable, watching Johnson trying to be apologetic (again) and contrite. He had the look of a man whose days are numbered.
Tai Chi was extra calming today and gave a perspective on the current troubled (and troubling) situations throughout the world.