Drilled Holes Stones- A Ancient Find?

                                            (Drilled hole in stone found in Overton area, Yarmouth County.)
Some thing I come across quite often on my 'looks arounds' are drilled holes in rocks and boulders. Often they are on the top of the stone, for what,I often wonder... A flag? Was these used for measuring distance with some ancient tool or for making territory for Native people.
Seems these have been found all over the globe. What do you think?

Link-

 Ancient drilled stone holes