It has been so long since I visited the Devils Arrows that I cannot remember whether the grooves appear on 'all four sides', as it were.

I have waited until I got my photies back to confirm that the Carlow stones do have grooves all the way around. To me, this does not seem entirely consistant with erosion on the bedding plane. Erosion on the bedding plane would imply erosion on just two opposite sides ... am I wrong?