The stones show the point of the horizon where the sun rises at the winter solstice. The distance between the stones is 5.1 m
The animation shows the shadow’s passage both 4 and 8 days prior to, as well as on the day of the winter solstice:
The gradient of the higher stone is in good alignment with the sun’s path. The two stones shows the exact point for the sunrise at the winter solstice.
Trees obscure the sun at the sunrise.