It was a hole and I had to crawl through it to install the extractor fan. I think I need to start Pilates in the new year to improve my contortions at work. The over cubicle light sits in the centre of the ducting for the inline extractor fan sited in the loft space above. The ducting leads towards the gable end where a 100mm core was made and a wind proof exterior vent grille put on the outside.