Dolerite Gateposts near Garnffoi

For the gate post lovers of the world (and Russia in particular) here is a picture of a pair of standing stones / gate posts at the roadside near Garnffoi, about a mile from Newport.  These stones are about 2m high, and they are very stable indeed -- so each one might well be about 3m long.  Note the twin holes drilled in each one -- rather too close together, one would have thought, for gate hinges.  Could it be that there was a sort of hooking mechanism, from which a detachable hurdle or gate could be easily removed and replaced again?  Advice from some old rural codgers would be appreciated....

While I am about it, I discovered this splendid gate today, up on the edge of Carningli Common.  Sadly, it was not hung onto bluestone pillars.......