Border Closure operation loren

When, what, why? Some info for me (us?) non-british . I know about the situation in general, but what was going on in this case?

It was not always possible to have troops on all the roads that ran from Northern Ireland into the South , so some roads into the south were barracaded with concrete blocks,barrels and large craters. The locals used to open up the barracades when nobody was around, so the army and the RUC used to close them again. This was always a dangerous job because it meant a lot of troops and police in one small place.
The dangers were booby traps and snipers etc.

Dangerous job indeed. And that was 80's? Or are these border closures still happening today?

This was around 1992. I dont think they bother now as most, if not all of the PVCP (Permanent Vehicle Check points) have been closed.